50 lines
779 B
Perl
Executable File
50 lines
779 B
Perl
Executable File
#! /usr/local/bin/perl -sw
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use vars qw($animal);
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use Parse::RecDescent;
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$grammar = q {
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object: thing[article=>'a'](s)
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| thing[article=>'the'](s)
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thing: <matchrule:$arg{article}>
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<matchrule:${\scalar reverse $::animal}>
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a: 'a'
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the: 'the'
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cat: 'cat' { print "meow\n"; $::animal = 'god' }
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dog: 'dog' { print "woof\n" }
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};
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unless( $parser = new Parse::RecDescent( $grammar ))
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{
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die "bad grammar; bailing\n";
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}
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$/ = "";
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while (defined ($input = <DATA>))
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{
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$::animal = reverse 'cat';
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print STDERR "parsing...\n";
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unless( defined $parser->object( $input ))
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{
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die "error in input; bailing\n";
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}
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print STDERR "...parsed\n";
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}
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__DATA__
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a cat
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a cat
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a cat
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a dog
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the cat
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the dog
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the dog
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the dog
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the dog
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a dog
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