I admit this example is a bit contrived, but it helps focus on what I'm trying to do...

Say I have a file like:

bang    !some text!
at      @more words@
percent %good stuff%
star    !not in stars!
[download]

I'm trying to match lines where the delimiter is specified by the keyword in the first column.

I can hard-code everything statically, like this:

#!/usr/bin/env perl6
use Test;

our grammar StatGrammar {
    rule TOP {
      [ <bang-line>    | <at-line>    | <hash-line> | <dollar-line>
      | <percent-line> | <caret-line> | <and-line>  | <star-line>   ]
    }

    regex    bang-line { ^    'bang' \s+ '!' (.*?) '!' \n? $ }
    regex      at-line { ^      'at' \s+ '@' (.*?) '@' \n? $ }
    regex    hash-line { ^    'hash' \s+ '#' (.*?) '#' \n? $ }
    regex  dollar-line { ^  'dollar' \s+ '$' (.*?) '$' \n? $ }
    regex percent-line { ^ 'percent' \s+ '%' (.*?) '%' \n? $ }
    regex   caret-line { ^   'caret' \s+ '^' (.*?) '^' \n? $ }
    regex     and-line { ^     'and' \s+ '&' (.*?) '&' \n? $ }
    regex    star-line { ^    'star' \s+ '*' (.*?) '*' \n? $ }
}

our class StatActions {
    method TOP($/) {
      make    $<bang-line>[0] if    $<bang-line>;
      make      $<at-line>[0] if      $<at-line>;
      make    $<hash-line>[0] if    $<hash-line>;
      make  $<dollar-line>[0] if  $<dollar-line>;
      make $<percent-line>[0] if $<percent-line>;
      make   $<caret-line>[0] if   $<caret-line>;
      make     $<and-line>[0] if     $<and-line>;
      make    $<star-line>[0] if    $<star-line>;
    }
}

sub static(Str $str) {
    StatGrammar.parse($str, :actions(StatActions)).made
}

is   static('bang  !one!' ), 'one',  'parse bang!one ok';
isnt static('bang  @one@' ), 'one',  'isnt  bang@one ok';
nok  StatGrammar.parse('bang @one@', :actions(StatActions)), 'nok';
[download]

But that feels kind of gross, and not very DRY...

I can also do this:

#!/usr/bin/env perl6
use Test;

our %sigils = (
    bang    => '!', at      => '@', hash    => '#', dollar  => '$',
    percent => '%', caret   => '^', and     => '&', star    => '*',
);

our grammar DynGrammar {
    regex TOP { ^ (\w+) \s+ (.*?)  \n? $ }
}

our class DynActions {
   method TOP($/) {
      if $1.match( rx/ ^ "{%sigils{$0}}" (.*?) "{%sigils{$0}}" $ / ) -
+> $match {
          make $match[0];
      }
   }
}

sub dyn(Str $str) {
    DynGrammar.parse($str, :actions(DynActions)).made
}

is   dyn('bang    !one!' ), 'one',  'parse bang!one ok';
isnt dyn('bang    @one@' ), 'one',  'isnt  bang@one ok';
nok  DynGrammar.parse('bang @one@', :actions(DynActions)), 'nok';
[download]

Which *ALMOST* works... Except that the mismatch, erm, "fails to fail".

Can anybody think of a way to either A: 'fail' a match from within an action, or B: move my pattern matching up into the grammar itself? (or C: tell me I'm going about it all wrong, and suggest a better way, hehe!)

Cheers! :-D

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