Lingua::Romana::Perligata -- Perl for the XXI-imum Century

Damian Conway

School of Computer Science and Software Engineering
Monash University
Clayton 3168, Australia u/~damian


This paper describes a Perl module -- Lingua::Romana::Perligata -- that makes it possible to write Perl programs in Latin. A plausible rationale for wanting to do such a thing is provided, along with a comprehensive overview of the syntax and semantics of Latinized Perl. The paper also explains the special source filtering and parsing techniques required to efficiently interpret a programming language in which the syntax is (largely) non-positional.


Compared to other languages (both modern and ancient), English has a comparatively weak lexical structure. Much of the grammatical load of an English sentence is carried by positional cues. A statement such as ``The boy gave the dog the food'' only makes sense because of the convention that the subject precedes the verb, which precedes the indirect object, which precedes the direct object. Changing the order -- ``The food gave the boy the dog'' -- changes the meaning.

Most programming languages use similar positional grammatical cues. The operation $maximum = $next is very different in meaning from $next = $maximum. Likewise, the function call push @my_assets, @your_money is not the same as push @your_money, @my_assets.

Generally speaking, older natural languages have richer lexical structures (such as inflexions for noun number and case) and therefore rely less on word order. For example, in Latin the statements Puer dedit cani escam and Escam dedit puer cani both mean ``The boy gave the dog the food''. Indeed, the more usual word order would be reverse Polish, with the verb coming last: Puer cani escam dedit.

This flexibility is possible because Latin uses inflexion, not position, to denote lexical roles. The lack of a suffix denotes that the boy (puer) is the subject; the -i ending indicates that the dog (cani) is the indirect object; whilst the -am ending indicates that the food (escam) is the direct object.

To say ``The food gave the boy the dog'', one might write: Puero canem esca dedit. Here, the -o ending denotes that the boy is now the indirect object, the -em ending indicates that the dog has become the direct object, whilst the -a ending indicates that the food is the subject.

A less positional programming language

There is no reason why programming languages could not also use inflexions, rather than position, to denote lexical roles. Perl already makes some use of this idea by requiring different prefixes to denote differing types of symbols: $ to denote a scalar, @ to denote an array, & to denote a subroutine, etc.

Indeed, there is no reason why certain built-in functions, such as bless, or the block form of map, or even push could not allow their arguments to be specified in any order, at least in cases where the prefixes (or the lack thereof) make the roles of each argument unambiguous:

        my $obj = bless 'Classname', \%obj;
        @squares = map @numbers {$_**2};
        push ('Moe', 'Larry', 'Curly') => @stooges;
Moreover, since the function names themselves are unambiguous in their role, there is no reason why their position need be fixed either:
        @squares = @numbers map {$_**2};
        ('Moe', 'Larry', 'Curly') => @stooges push;
Perl already allows a modicum of this flexibility in the form of statement modifiers:
        if ($next > $max) { $max = $next }
        # the same as...
        $max = $next if $next > $max;
This paper describes a new module -- Lingua::Romana::Perligata -- that explores an alternative syntactic binding for Perl, using inflexions based on classical Latin grammar. These inflexions subsume the function of the standard Perl $/@/%/& prefixes and support the new concept of semantic roles, which allows far greater freedom in the specification of functions, operations, and their respective arguments.

Semantic roles

Most of Perl's rich variety of operators provide an assignment variant: += for +, .= for ., ||= for ||, etc. Thus, nearly half of Perl's operators produce some change in one of their arguments. Likewise, many built-in Perl functions (push, pop, open, etc.) modify one of their arguments.

In both cases, the operand or argument to be modified is denoted positionally -- it is always the left operand or the first argument. Furthermore this argument is always ``implicitly enreferenced'', as if it had a \$ or \@ prototype.

Thus, in Perl, operands and arguments have one of two semantic roles: target or data. A target is passed by reference and is modified during the evaluation of an operation or function. Data are passed by value (though that value itself may be a reference) and they control or ``fuel'' the modification of the target.

In this model, it is possible to recast almost all built-in Perl functions and operations as procedures of exactly two arguments: a single reference (the target) and a single list (the data):

        _sysopen( -target=>\*FILE, -data=>[$filename,$mode,$perms] );
        _push( -target=>\@stooges, -data=>['Moe', 'Larry', 'Curly'] );
        _pop( -target=>\@stack, -data=>[] );
        _assign( -target=>\$max, -data=>[$nextval] )
                if _num_less_than( -target=>undef, -data=>[$max, $nextval] );
        _assign( -target=>\$now, -data=>[ _time(-target=>undef, -data=>[]) ]);
Note that, for many functions, either or both of these two standard arguments may be null.

Mapping the model to Latin

To map this simplified model of Perl onto an inflexion-based syntax, it is necessary to choose an inflexion scheme that differentiates the three components of each function: name, target, and data.

Consider the assignment of a list to an array:

        @gunslingers = ( @good, @bad, $Ugly );
In semantic role notation that is:
        _assign( -target=>\@gunslingers, -data=>[@good, @bad, $Ugly] );
In English, this would be expressed:
        Assign gunslingers goodies and baddies and Mr Ugly.
The imperative verb ``assign'' specifies the action to be performed. The noun ``gunslingers'' specifies the indirect (or dative) object of the action. In other words, it is the recipient of the effect of the action -- the target. The phrase ``goodies and baddies and uglies'' specifies the direct object of the action -- that which is to be assigned. In other words, the data. The direct and indirect objects are only distinguished by the order in which they appear: indirect object first.

The English version also uses a plural inflexion on ``goodies'' and ``baddies'', much in the same way that Perl uses the @ prefix to indicate the multiplicity of the objects involved.

In Latin, the same instruction would be (loosely) rendered:

        Bonos tum malos tum Foedum pugnatoribus da.
Here the direct objects are bonos (``the good (people)'', accusative plural), malos (``the bad (people)'', accusative plural) and Foedum (``Mr Ugly'', accusative singular). The indirect object is pugnatoribus (``fighters'', dative plural) and the verb is da (``give'', present imperative). The conjunction tum means ``and then'', and conveys the significance of the order of the direct objects.

Unlike the English ``-s'' ending, the various Latin suffixes (-os, -um, -ibus) specify both the number and the role (or ``case'') of the nouns they inflect. This means that the positions of the various objects, and indeed of the verb itself, do not matter. The same sentence could equally well be written:

        Pugnatoribus da bonos tum malos tum Foedum.
        Da bonos tum malos tum Foedum pugnatoribus.
Semantically, all of these variants (and any other permutations of the verb and its objects) are equivalent to the same target/data model:
        _assign( -target=>\@gunslingers, -data=>[@good, @bad, $Ugly] );
and hence are equivalent to the standard Perl:
        @gunslingers = ( @good, @bad, $Ugly );
Thus it is possible to write Perl programs in Latin.


The Lingua::Romana::Perligata module provides the necessary translation services to allow Perl programs to be written using a syntactic binding (perligatus) modelled on the ancient lingua Romana. To distinguish it from regular Perl, this binding -- and any code specified in it -- is henceforth referred to as ``Perligata''.


To simplify the mind-numbingly complex rules of declension and conjugation that govern inflexions in Latin, Perligata treats all user-defined scalar and array variables as neuter nouns of the second declension -- singular for scalars, plural for arrays. This minimizes the number of suffixes that must be remembered.

Hashes represent something of a difficulty in Perligata, as Latin lacks an obvious way of distinguishing these ``plural'' variables from arrays. The solution that has been adopted is to depart from the second declension and represent hashes as masculine plural nouns of the fourth declension.

Hence, the type and role of all types variables are specified by their number and case, as indicated in Table 1.

When elements of arrays and hashes are referred to directly in Perl, the prefix of the container changes from @ or % to $. So it should not be surprising that Perligata also makes use of a different inflexion to distinguish these cases.

Indexing operations such as $array[$elem] or $hash{$key} might be translated as ``elem of array'' or ``key of hash''. This suggests that when arrays or hashes are indexed, their names should be rendered in the genitive (or possessive) case. Multi-level indexing operations ($array[$row][$column]) mean ``column of row of array'', and hence the first indexing variable must also be rendered in the genitive. Table 1 also summarizes this role.

Table 1: Perligata variables
Number, Case, and Declension
nextum accusative singular 2nd $next scalar data
nexta accusative plural 2nd @next array data
nextus accusative plural 4th %next hash data
nexto dative singular 2nd \$next scalar target
nextis dative plural 2nd \@next array target
nextibus dative plural 4th \%next hash target
nexti genitive singular 2nd [$next] indexed scalar
nextorum genitive plural 2nd $next[] indexed array
nextuum genitive plural 4th $next{} indexed hash

In other words, scalars are always singular nouns, arrays and hashes are always plural (but of different declensions), and the case of the noun specifies its role: accusative for data, dative for target, genitive when being indexed.

The common punctuation variables $_ and @_ are special cases. $_ is often the value under implicit consideration (e.g. in pattern matches, or for loops) and so it is rendered as ``this thing'': hoc in the data role, huic in the target role, huius when indexed.

Similarly, @_ is implicitly the list of things passed into a subroutine, and so is rendered as ``these things'': haec in the data role, his in the target role, horum when indexed.

Other punctuation variables take the Latin forms of their equivalents (see Appendix A), often with a large measure of poetic licence. For example, in Perligata, $/ is rendered as ianitorem or ``gatekeeper''.

The ``numeral'' variables -- $1, $2, etc. -- are rendered as synthetic compounds: parprimum (``the equal of the first''), parsecundum (``the equal of the second''), etc. When indexed, they take their genitive forms: parprimi, parsecundi, etc. Since they cannot be directly modified as the target of an action, they have no dative forms.

my, our, and local

In Perligata, the my modifier is rendered -- not surprisingly -- by the first person possessive pronouns: meo (conferring a scalar context) and meis (for a list context). Note that the modifier is always applied to a dative, and hence is itself declined in that case. Thus:
        meo varo haec da.                # my $var = @_;
        meis varo haec da.               # my ($var) = @_
        meis varis haec da.              # my @var = @_;
Similarly the our modifier is rendered as nostro or nostris, depending on the desired context.

The Perl local modifier is loco or locis in Perligata:

        loco varo haec da.               # local $var = @_;
        locis varo haec da.              # local ($var) = @_
        locis varis haec da.             # local @var = @_;
This is particularly felicitous: not only is loco the Latin term from which the word ``local'' derives, it also means ``in place of'' (as in: in loco parentis). This meaning is much closer to the actual behaviour of the local modifier, namely to temporarily install a new symbol table entry in place of the current one.


Functions, operators, and user-defined subroutines are represented as verbs or, in some situations, verbal nouns. Here, the inflexion of the verb determines not only its semantic role, but also its call context.

User-defined subroutines are the simplest group. To avoid ambiguity, they are all treated as verbs of the third conjugation. Table 2 illustrates the various usages for a user-defined subroutine count().

Table 2: Perligata subroutines
Number, Mood, etc
countere infinitive sub count definition -
counte imperative sing. count() call void
countementum acc. sing. resultant count() call-data scalar
countementa acc. plur. resultant count() call-data list
countemento dat. sing. resultant count() call-target scalar
countementis dat. plur. resultant count() call-target  list

The use of the infinitive as a subroutine definition is obvious: accipere would tell Perligata how ``to accept''; spernere, how ``to reject''. So countere specifies how ``to count''.

The use of the imperative for void context is also straightforward: accipe commands Perligata to ``accept!'', sperne tells it to ``reject!'', and counte bids it ``count!''. In each case, an instruction is being given (and in a void context too, so no backchat is expected).

Handling scalar and list contexts is a little more challenging. The corresponding Latin must still have verbal properties, since an action is being performed upon objects. But it must also have the characteristics of a noun, since the result of the call will itself be used as the object (i.e. target or data) of some other verb. Fortunately, Latin has a rich assortment of verbal nouns -- far more than English -- that could fill this role.

Since it is the result of the subroutine call that is of interest here, the best solution was to use the -ementum suffix, which specifies the (singular, accusative) outcome of an action. This corresponds to the result of a subroutine called in a scalar context and used as data. For a list data context, the plural suffix -ementa is used, and for targets, the dative forms are used: -emento and -ementis. Note that these endings are completely consistent with those in Table 1.

Built-in functions and operators

Built-in operators and functions could have followed the same pattern as subroutines. For example shift might have been shifte in a void context, shiftementa when used as data in an array context, shiftemento when used as a target in a scalar context, etc.

However, Latin already has a perfectly good verb with the same meaning as shift: decapitare (``to behead''). Unfortunately, this verb is of the first conjugation, not the second, and hence has the imperative form decapita, which makes it look like a Perligata array in a data role.

Orthogonality has never been Perl's highest design criterion, so Perligata follows suit by eschewing bland consistency in favour of aesthetics. All Perligata keywords -- including function and operator names -- are therefore specified as correct Latin verbs, of whatever conjugation is required. Table 3 shows a selection of these, whilst Appendix A contains the full list of Perligata keywords.

Table 3: Sample Perligata built-in functions and operators 
Operator/ function
Rendered as
Void context
Scalar data
List data
+ "add" adde addementum addementa 
= "give" da damentum damenta 
. "conjoin" sere serementum serementa 
.. "enlist" conscribe conscribementum conscribementa 
shift "behead" decapita decapitamentum decapitamenta 
push "stack" cumula cumulamentum cumulamenta 
pop "unstack" decumula decumulamentum decumulamenta 
grep "winnow" vanne vannementum vannementa 
print "write" scribe scribementum scribementa 
write "write under" subscribe subscribementum subscribementa 
die "die" mori morimentum morimenta 

Note, however, that consistency has not been entirely forsaken. The back-formations of inflexions for scalar and list context are entirely regular, and consistent with those for user-defined subroutines (Table 2).

A few Perl built-in functions -- pos, substr, keys -- can be used as lvalues. That is, they can be the target of some other action (typically of an assignment). In Perligata such cases are written in the dative singular (since the lvalues are always scalar). Note too that, because an assignment to an lvalue function modifies its first argument, that argument must be a target too, and hence must be written in the dative as well.


        nexto stringum reperimentum da.     # $next = pos $string;
        nextum stringo reperimento da.      # pos $string = $next;
        inserto stringum tum unum tum duo excerpementum da.
                                    # $insert = substr($string,1,2);
        insertum stringo unum tum duo excerpemento da.
                                    # substr($string,1,2) = $insert;
        keyis hashus nominamentum da        # @keys = keys %hash;
        keya hashibus nominamento da        # keys %hash = @keys;

Blocks and control structures

Natural languages generally use some parenthetical device -- such as parentheses, commas, or (as here) dashes -- to group and separate collections of phrases or statements.

Some such mechanism would be an obvious choice for denoting Perligata code blocks, but there is a more aesthetically pleasing solution. Perl's block delimiters ({..}) have two particularly desirable properties: they are individually short, and collectively symmetrical. It was considered important to retain those characteristics in Perligata.

In Latin, the word sic has a sense that means ``as follows''. Happily, its contranym, cis, has the meaning (among others) ``to here''. The allure of this kind of wordplay being impossible to resist, Perligata delimits blocks of statements with these two words. For example:

        sic                                     # {
            loco ianitori.                     #   local $/;
            dato fonti perlegementum da.        #   $data = <DATA>;
        cis                                     # }
Control structures in Perligata are rendered as conditional clauses, as they are in Latin, English, and Perl. And as in those other languages, they may precede or follow the code blocks they control. Table 4 summarizes the control structures Perligata provides.
Table 4: Perligata control structures
si ... fac if ... 
nisi ... fac unless ... 
dum ... fac while ...
donec ... fac until ...
per (quisque) ... in ... fac for(each) ... 
posterus next 
ultimus last 
reconatus redo 
confectus continue 

The trailing fac is the imperative form of facere (``to do'') and is used as a delimiter on the control statement's condition.

The choice of dum and donec is completely arbitrary, since Latin does not distinguish ``while'' and ``until'' as abstractions in the way English does. Dum and donec each mean both ``while'' and ``until'', and Latin relies on context (i.e. semantics) to distinguish them. This is impractical for Perligata, so it always treats dum as while and donec as until. This choice was made in order to favour the shorter term for the more common type of loop.

The choice of confectus for continue seeks to convey the function of the control structure, not the literal meaning of the English word. That is, a continue block specifies how to complete (conficere) an iteration.

Perligata only supports the pure iterative form of for(each), not the C-like three-part syntax. Because:

        foreach $var (@list)...
means ``for each variable in the list...'', the scalar variable must be in the accusative (as it is governed by the preposition ``for''), and the list must be in the ablative (denoting inclusion). Fortunately, in the second declension, the inflexion for ablatives is exactly the same as for datives, giving:
        per quisque varum in listis...
This means that no extra inflexions have to be learned just to use the per loop. Better still, the list (listis) looks like a Perligata array variable in a target role, which it clearly is, since its contents may be modified within the loop.

Miscellaneous other features



Numeric literals in Perligata are rendered by Roman numerals -- I, II, III, IV...XV...XLII, etc. However, the first 10 numbers may also be referred to by name: unum, duo, tres, quattuor, quinque, sex, septem, octo, novem, decem. Zero, for which there is no Latin numeral, is rendered by nullum (``no-one''). Nihil (``nothing'') might have been a closer rendering, but it is indeclinable and hence indistinguishable in the accusative and genitive.

When a numeric literal is used in an indexing operation, it must be an ordinal (``first of'', ``second of'', etc). The first ten ordinals are named: primum, secundum, tertium, quartum, quintum, sextum, septimum, octavum, nonum, decimum (in the accusative, of course, since they are always data). Ordinals greater than ten are represented by their corresponding numeral with the suffix -imum: XVimum (``15th''), XLIIimum (``42nd''), etc. By analogy, ordinal zero is rendered by the invented form nullimum.

In a multi-level indexing operation, ordinals may need to be specified in the genitive: nulli, primi, secundi, tertii, quarti...XVimi...XLIIimi, etc.

For example:

would be:
        septimum noni tertii primi unimatrixorum
        # seventh of ninth of third of first of unimatrix
Note that the order of the genitives is significant here, and is the reverse of that required in Perl.

Floating point numbers are expressed in Perligata as Latin fractions:

        unum quartum                    # 0.25
        MMMCXLI Mimum                 # 3.141
Note that the numerator is always cardinal and the denominator ordinal (``one fourth'', ``3141 1000ths''). Technically, both should also be in the feminine gender -- una quarta, MMMCXLI Mimae -- but this Latin rule is not enforced in Perligata.


Classical Latin does not use punctuation to denote direct quotation. Instead the verb inquit (``said'') is used to report a direct utterance. Hence in Perligata, a literal character string is constructed, not with quotation marks, but by invoking the verbal noun inquementum (``the result of saying''), with a data list of literals to be interpolated. For example:
        print STDOUT 'Enter next word:';
        Enter tum next tum word inquementum tum biguttam egresso scribe.
Note that the arguments to inquementum are special in that they are treated as literals. Punctuation strings have special names, such as lacunam (``a hole'' -> space), stadium (``a stride'' -> tabspace), novumversum (``new verse'' -> newline), or biguttam (``two spots'' -> colon).

Perligata does not provide an interpolated quotation mechanism. Instead, variables must be concatenated into a string. So:

        print STDERR "You entered $word\n";
        You tum entered inquementum tum wordum tum novumversum oraculo scribe.


To create a reference to a variable in a data role (target role variables are automatically enreferenced), the variable is prefaced with the preposition ad (``to''). To create a reference to a subroutine, the associated verb is inflected with the accusative suffix -torem (``one who...'') to produce the corresponding noun-of-agency.

For example:

        val inquementum datuum ad datum da.       # $dat{val} = \$data;
        arg inquementum datuum ad arga da.        # $dat{arg} = \@arg;
        act inquementum datuum functorem da.      # $dat{act} = \&func;
A special case of this construction is the anonymous subroutine constructor factorem (``one who does...''), which is the equivalent of sub {...} in Perl:
        anonymo da factorem sic haec mori cis.    # $anon = sub { die @_ };
As in Perl, such subroutines may be invoked by concatenating a call specifier to the name of the variable holding the reference:
        anonymume nos tum morituri inquementum.   # &$anon('Nos morituri');
Note that the variable holding the reference (anonymum) is being used as data, so it is named in the accusative.

In the few cases where a subroutine reference can be the target of an action, the dative suffix (-tori) is used instead:

        benedictum functori classum.              # bless \&func, $class;
        benedictum factori sic mori cis classum.  # bless sub{die}, $class;

Boolean logic

Perl's logical conjunctive and disjunctive operators come in two precedences, and curiously, so do those of Latin. The higher precedence Perl operators -- && and || -- are represented in Perligata by the emphatic Latin conjunctions atque and vel respectively. The lower precedence operators -- and and or -- are represented by the unemphatic conjunctive suffixes -que and -ve. Hence:
	resulto damentum foundum atque defum.    # $result = $found && $def;
        resulto damentum foundum defumque.       # $result = $found and $def;
        resulto damentum foundum vel defum.      # $result = $found || $def;
        resulto damentum foundum defumve.        # $result = $found or $def;
Note that, as in Latin, the suffix of the unemphatic conjunction is always appended to the first word after the point at which the conjunction would appear in English. Thus:
        $result = $val or max($1,$2);
is rendered as:
        resulto damentum valum parprimumve tum parsecundum maxementum.
Proper Latinate comparisons would be odious in Perligata, because they require their first argument to be expressed in the nominative and would themselves have to be indicative. This would, of course, improve the positional independence of the language even further, allowing:
        si valus praecedit datum...              # if $val < $dat...
        si praecedit datum valus...              # if $val < $dat...
        si datum valus praecedit...              # if $val < $dat...
Unfortunately, it also introduces another set of case inflexions and another verbal suffix. Worse, it would mean that noun suffixes are no longer unambiguous. In the 2nd declension, the nominative plural ends in the same -i as the genitive singular, and the nominative singular ending (-us) is the same as the accusative plural suffix for the fourth declension. So if nominatives were used, scalars could no longer always be distinguished from arrays or from hashes, except by context.

To avoid these problems, Perligata represents the equality and simple inequality operators by three pairs of verbal nouns as described in Table 5.

Table 5: Perligata comparison operators
aequalitam "equality (of...)" == 
aequalitas "equalities (of...)" eq 
praestantiam "precedence (of...)" <
praestantias "precedences (of...)" lt 
comparitiam "comparison (of...)" <=> 
comparitias "comparisons (of...)" cmp 

Each operator takes two data arguments, which it compares:

        si valum tum datum aequalitam...               # if $val == $dat...
        si valum praestantias datum...                 # if $val lt $dat...
        digere sic aum comparitiam bum cis lista.      # sort {$a<=>$b} @list;
Note that although digere looks like an infinitive (i.e. a subroutine definition) it is in fact the imperative of digerere (``to sort'') and is the Perligata keyword for sort. The philosophically inclined might choose to think of the confusion this engenders as a form of Instant Justice visited upon those who use sort in a void context.

The effects of the other comparison operators -- &gt;, &lt;=, !=, ne, ge, etc. -- are all achieved by appropriate ordering of the two arguments and combination with the the logical negation operator non:

        si valum datum non aequalitam...         # if $val != $dat...
        si datum praestantiam valum...           # if $val > $dat...
        si valum non praestantias datum...       # if $val ge $dat...

Packages and classes

The Perligata keyword to declare a package is domus, literally ``the house of''. In this context, the name of the class follows the keyword and is treated as a literal; as if it were the data argument of an inquementum.

To explicitly specify a variable or subroutine as belonging to a package, the preposition intra (``within'') is used. To call a subroutine as a method of a particular package (or of an object), the preposition apud (``of the house of'') is used.

The Perl bless function is benedice in Perligata, but almost invariably used in the scalar data role: benedictum.


        domus Specimen.                        # package Specimen;
        newere                                      # sub new
        sic                                         # {
            meis datibus.                           #   my %data;
            counto intra Specimen
                postincresce.                       #   $Specimen::count++;
            datibus nullum horum benedictum.        #   bless \%data, $_[0];
        cis                                         # }
        printere                                    # sub print
        sic                                         # {
            modus tum indefinitus inquementum mori. #   die 'method undefined';
        cis                                         # }
        domus princeps.                             # package main;
        meo objecto da                              # my $object =
                newementum apud Specimen.      #       Specimen->new;
        printe apud objectum;                       # $object->print;

Putting it all together -- a Greek algorithm in Latin

The Sieve of Eratosthenes is one of oldest well-known algorithms. As the better part of Roman culture was ``borrowed'' from the Greeks, it is perhaps fitting that the first ever Perligata program should be as well:
        #! /usr/local/bin/perl -w
        use Lingua::Romana::Perligata;
        maximum inquementum tum biguttam egresso scribe.
        meo maximo vestibulo perlegamentum da.
        da duo tum maximum conscribementa meis listis.
        dum listis decapitamentum damentum nexto
            fac sic
                nextum tum novumversum scribe egresso.
                lista sic hoc recidementum nextum cis vannementa da listis.
The use Lingua::Romana::Perligata statement causes the remainder of the program to be translated into the following Perl:
        print STDOUT 'maximum:';                  
        my $maxim = <STDIN>;                     
        my (@list) = (2..$maxim);
        while ($next = shift @list)             
                print STDOUT $next, "\n";
                @list = grep {$_ % $next} @list; 
Note in the very last Perligata statement (lista sic hoc...da listis) that the use of inflexion distinguishes the @list that is grep'ed (lista) from the @list that is assigned to (listis), even though each is at the ``wrong'' end of the statement, compared with the Perl version.

The implementation of the Lingua::Romana::Perligata module

The module itself is a very simple example of a source filter, and makes use of Paul Marquess's Filter::Util::Call module. The Perligata parser is invoked from a single subroutine, which is called as a filter on the source code, as described in the following sections.


The Filter::Util::Call module greatly simplifies the task of pre-filtering source code. A filtering module that uses Filter::Util::Call simply adds the command filter_add({}) to its import subroutine. Then when the filtering module is itself used in some code, Filter::Util::Call looks in the filtering module's namespace for a subroutine called filter, which it calls. That filter subroutine can access the source code from the file that called the filtering module, and can modify that code as appropriate. Whatever string is in the variable $_ when the filter subroutine returns is passed to the compiler as the final program source.


For Lingua::Romana::Perligata, the filter subroutine conforms to the usual structure of a grammar-based parser/translator. It first invokes a tokenizer to break the Perligata source code into a sequence of tokens.

The tokenizer is very simple: it just splits the source on whitespace or on a period, and then classifies each word in the resulting list by matching it against a series of increasingly general patterns. Keywords are tested first, followed by numbers and numerals, punctuation variables, user-defined functions in scalar and list contexts, user-defined subroutines in void contexts, variables in a target role (i.e. datives), and finally variables in a data role (accusatives),

As each word is classified, it is converted to an object of the corresponding token type -- Keyword, Number, Var, Sub, etc. Each object stores the original word and its corresponding Perl construct. For example, the sequence dum maxo maxa maxamentum damentum would yield a list equivalent to:

            bless({ raw=>'dum',        perl=>'while' }, 'Conditional'     ),
            bless({ raw=>'maxo',       perl=>'$max'  }, 'Noun_Dative'     ),
            bless({ raw=>'maxa',       perl=>'@max'  }, 'Noun_Accusative' ),
            bless({ raw=>'maxamentum', perl=>'&max'  }, 'Verb_Resultative'),
            bless({ raw=>'da',         perl=>'='     }, 'Verb_Imperative  ),
These objects then form a stream of tokens that is passed to the parser.


The position-independence of much of the Perligata grammar makes the task of parsing it quite challenging when using standard tools, which are typically predicated on lexical components appearing in rigidly defined sequences.

For example, to write a rule that matches Perligata subroutine calls, the following is required:

        Action: Dative AccusativeList Verb
              | AccusativeList Dative Verb
              | AccusativeList Verb Dative
              | Dative Verb AccusativeList
              | Verb Dative AccusativeList
              | Verb AccusativeList Dative
              | Accusative Verb Accusative
              | Dative Verb
              | AccusativeList Verb
              | Verb Dative
              | Verb AccusativeList
              | Verb
The difficulties are further compounded by the fact that targets and data can also be (the results of) other position-independent subroutine calls.

This produces a left-recursive grammar with an unusually large number of shift/reduce and reduce/reduce ambiguities (over 100 of each), which makes the grammar very sensitive to subrule precedence and to the ordering of productions within each rule. Appendix B shows the full grammar.

To cope efficiently with these constraints, an LALR(1) parser was built using François Désarménien's excellent Parse::Yapp module.

Translation and execution

Each rule of the Perligata grammar contains an embedded action. Collectively these actions construct a full parse tree for the source code as the grammar parses it. Each node in the tree is a blessed object belonging to a class that represents the corresponding Perl construct. For example, after it has been parsed, the fragment dum maxo maxa maxamentum damentum will have been converted to the following tree:
        bless( {
            condition =>
              bless( {
                 target =>
                    bless( { raw => 'maxo', perl => '$max' }, 'Var_Target'),
                 data =>
                    bless( {
                       raw  => 'maxamentum', perl => '&max',
                       data => [
                          bless( { raw=>'maxa', perl=>'@max'  }, 'Var_Data'),
                    }, 'SubCall'),
                }, 'Assignment'),
             block =>
        }, 'WhileLoop');
Once the tree is constructed, the equivalent Perl code is obtained by calling the method codify() on the root node of the tree. This recursively invokes the codify() methods of all the subnodes in the tree, each of which returns a string containing a Perl code fragment corresponding to the subtree at that node. By concatenating these fragments, a string containing the full Perl program is generated. This string is assigned to $_ at the end of the filter() subroutine, to be compiled and executed automatically by Filter::Util::Call.


Latin is a surprisingly good fit for Perl. The rich case structure provides an abundance of plausible mappings for Perl data types and subroutine calls, especially when Perl's own eclectic syntax and semantics are mapped onto the more regular ``action/target/data'' model.

The use of inflexion to denote semantic roles in a programming language offers an interesting variation from the ubiquity of positional syntax, replacing the requirement to recall syntactic rules with the requirement to remember suffixes. Which of these two tasks is easier will probably vary from programmer to programmer.

With the release of this module on the CPAN, the author looks forward to the advent of truly epic Perl poetry.


Special thanks to John Crossley, Tom Christiansen, and Bennett Todd, for their invaluable feedback and suggestions. And my enduring gratitude to David Secomb and Deane Blackman for their patience in helping me struggle with the perplexities of the lingua Romana.

Appendix A: Perligata dictionary

This appendix lists the complete Perligata vocabulary, except for Roman numerals (I, II, III, etc.)

In each of the following tables, the three columns are always the same: ``Perl construct'', ``Perligata equivalent'', ``Literal meaning of Perligata equivalent''.

Generally, only the accusative form is shown for nouns and adjectives, and only the imperative for verbs.

Table A1: Values and variables

0 nullum "no-one"
1 unum "one"
2 duo "two"
3 tres "three"
4 quattuor "four"
5 quinque "five"
6 sex "six"
7 septem "seven"
8 octo "eight"
9 novem "nine"
10 decem "ten"
1/2 secundum "second"
1/3 tertium "third"
1/4 quartum "fourth"
1/5 quintum "fifth"
1/6 sextum "sixth"
1/7 septimum "seventh"
1/8 octavum "eighth"
1/9 nonum "ninth"
1/10 decimum "tenth"
$1 parprimum "equal of the first"
$2 parsecundum "equal of the first"
$3 partertium "equal of the third"
$4 parquartum "equal of the fourth"
$5 parquintum "equal of the fifth"
$6 parsextum "equal of the sixth"
$7 parseptimum "equal of the seventh"
$8 paroctavum "equal of the eighth"
$9 parnonum "equal of the ninth"
$10 pardecimum "equal of the tenth"
$/ ianitorem "gatekeeper"
$#var admeta "measure out"
$_ hoc/huic "this thing"
@_ his/horum "these things"
":" biguttam "two spots"
" " lacunam "a gap"
"\t" stadium "a stride"
"\n" novumversum "new line"
local loco "in place of"
my meo "my"
our nostro "our"
main princeps "principal"


Table A2: Quotelike operators

'' inque "say"
q// inque "say"
m// compara "match"
s/// substitue "substitute"
tr/// converte "translate"
y/// converte "translate"


Table A3: Mathematical operators and functions

+ adde "add"
- deme "subtract"
- nega "negate"
* multiplica "multiply"
/ divide "divide"
% recide "lop off"
** eleva "raise"
++ preincresce "increase beforehand"
++ postincresce "increase afterwards"
-- predecresce "decrease beforehand"
-- postdecresce "decrease afterwards"
abs priva "strip from"
atan2 angula "create an angle"
sin oppone "oppose"
cos accuba "lie beside"
int decolla "behead"
log succide "log a tree"
sqrt fode "root into"
rand conice "guess, cast lots"
srand prosemina "to scatter seed"


Table A4: Logical and comparison operators

! non "general negation"
&& atque "empathic and"
|| vel "emphatic or"
and -que "and"
or -ve "or"
< praestantiam "precedence of"
lt praestantias "precedences of"
<=> comparitiam "comparison of"
cmp comparitias "comparisons of"
== aequalitam "equality of"
eq aequalitas "equalities of"


Table A5: Strings

chomp morde "bite"
chop praecide "cut short"
chr inde "give a name to"
hex senidemi "sixteen at a time"
oct octoni "eight at a time"
ord numera "number"
lc deminue "diminish"
lcfirst minue "diminish"
uc amplifica "increase"
ucfirst amplia "increase"
quotemeta excipe "make an exception"
crypt huma "inter"
length meta "measure"
pos reperi "locate"
pack convasa "pack baggage"
unpack deconvasa "unpack"
split scinde "split"
study stude "study"
index scruta "search"
join coniunge "join"
substr excerpe "extract"


Table A6: Scalars, arrays, and hashes

defined confirma "verify"
undef iani "empty, make void"
scalar secerna "to distinguish, isolate"
reset lusta "cleanse"
pop decumula "unstack"
push cumula "stack"
shift decapita "behead"
unshift capita "crown"
splice iunge "splice"
grep vanne "winnow"
map applica "apply to"
sort digere "sort"
reverse retexe "reverse"
delete dele "delete"
each quisque "each"
exists adfirma "confirm"
keys nomina "name" 
values argue "to disclose the contents"


Table A7: I/O related

open evolute "open a book"
close claude "close a book"
eof extremus "end of"
read lege "read"
getc sublege "pick up something"
<>/readline perlege "read through"
print scribe "write"
printf describe "describe"
sprintf rescribe "rewrite"
write subscribe "write under"
format pinge "paint"
formline distingue "intersperse"
pipe inriga "irrigate"
tell enunta "tell"
seek conquire "to seek out"
STDIN vestibulo "an entrance"
STDOUT egresso "an exit"
STDERR oraculo "a place were doom is pronounced"
DATA fonti "a well-spring"


Table A8: Control

{...} sic...cis "as here"
do fac "do"
sub {...} factorem sic...cis "one who does as here"
eval aestima "evaluate"
exit exi "exit"
for per "for"
foreach per quisque "for each"
goto adi "go to"
if si "if"
return redde "return"
unless nisi "if not"
until donec "until"
while dum "while"
wantarray deside "want"
last ultimus "final"
next posterus "following"
redo reconatus "trying again"
continue confectus "complete"
die mori "die"
warn mone "warn"


Table A9: Packages, classes, and modules

-> apud "of the house of"
:: intra "within"
bless benedice "bless"
caller memora "recount a history"
package domus "house of "
ref agnosce "identify"
tie liga "tie"
tied exhibe "display something"
untie solve "to untie"
require require "require"
use ute "use"


Table A10: System and filesystem interaction

chdir demigrare "migrate"
chmod permitte "permit"
chown vende "sell"
fcntl modera "control"
flock confluee "flock together"
glob inveni "search"
ioctl impera "command"
link copula "link"
unlink decopula "unlink"
mkdir aedifica "build"
rename renomina "rename"
rmdir excide "raze"
stat exprime "describe"
truncate trunca "shorten"
alarm terre "frighten"
dump mitte "drop"
exec commuta "transform"
fork furca "fork"
kill interfice "kill"
sleep dormi "sleep"
system obsecra "entreat a higher power"
umask dissimula "mask"
wait manta "wait for"


Table A11: Miscellaneous operators

, tum "and then"
. sere "conjoin"
.. conscribe "enlist"
\ ad "towards"
= da "give"

Appendix B: Perligata grammar

Script:         Statement(s)

Statement       ( Conditional | Imperative | Data | Target ) '.'

Conditional:      Control Block
                | Imperative Control

Control:          'dum'   Data  'fac'                      # while
                | 'donec' Data  'fac'                      # until
                | 'si'    Data  'fac'                      # if
                | 'nisi'  Data  'fac'                      # unless
                | /per (quisque)?/ NOUN_ACCUSATIVE(?)
                                   'in' Target 'fac'       # foreach A (B)

Block:            'sic'  Script  'cis'

Imperative:       Data Verb Data
                | Target Datalist Verb
                | Datalist Target Verb
                | Datalist Verb Target(?)
                | Target Verb Datalist(?)
                | Verb Target Datalist(?)
                | Verb Datalist Target(?)
                | Verb

Target:           NOUN_DATIVE
                | POSSESSIVE  NOUN_DATIVE               # my $A, local @B, etc.
                | Block
                | Data  Resultative_dative  Data
                | Target  Datalist  Resultative_dative
                | Datalist  Target  Resultative_dative
                | Datalist  Resultative_dative  Target(?)
                | Target  Resultative_dative  Datalist(?)
                | Resultative_dative  Target  Datalist(?)
                | Resultative_dative  Datalist(?)  Target(?)
                | Target  'intra'  Accusative           # B::A
                | Target  'apud'  Dative                # B->A
                | Target NOUN_GENITIVE                  # B[A]
                | 'factori' Block                       # sub {...}

Accusative:       NOUN_ACCUSATIVE
                | 'ad'  Accusative                      # \A
                | Accusative  'intra'  Accusative       # B::A
                | Accusative  'apud'  Accusative        # B->A
                | Accusative  NOUN_GENITIVE             # B[A]
                | 'factorem' Block                      # sub {...}

Data:             Accusative
                | 'nega'  Data                          # -A
                | 'non'  Data                           # !A
                | Data  Resultative_accusative  Data
                | Target  Datalist  Resultative_accusative
                | Datalist  Target  Resultative_accusative
                | Datalist  Resultative_accusative  Target(?)
                | Target  Resultative_accusative  Datalist(?)
                | Resultative_accusative  Target  Datalist(?)
                | Resultative_accusative  Datalist(?)  Target(?)

Verb:             VERB
                | Verb  'intra'  Accusative             # B::A()
                | Verb  'apud'  Dative                  # B->A()

                | Resultative_dative  'intra'  Accusative       
                | Resultative_dative  'apud'  Dative

                | Resultative_accusative  'intra'  Accusative   
                | Resultative_accusative  'apud'  Dative        

Datalist:         Datalist  'tum'  Data
                | Data