use strict;

use Parse::RecDescent;

$::RD_ERRORS = 1; # kill parser if it encounters an error
$::RD_WARN   = 1; # enable warnings
$::RD_HINT   = 1; # helpful hints

my $grammar = << 'GRAMMAR';
		
		seq: start codon(s) stop /^\Z/ 
		
		start: met
			
		stop: amber | ochre | opal 
		
		codon:  leu | phe | cys | trp | tyr | val | met |
				gly | ala | glu | asp | pro | arg | lys |
				his | gln | ser | thr | ile | asn 

		lys: A A pur { print "$item[0] " }
		asn: A A pyr { print "$item[0] " }
		ile: A U pyr { print "$item[0] " }
		thr: A C base { print "$item[0] " }
		met: A U G { print "$item[0] " }
		ser: A G pyr { print "$item[0] " }
		gln: C A pur { print "$item[0] " }
		his: C A pyr { print "$item[0] " }
		arg: C G base | A G pur { print "$item[0] " }
		pro: C C base { print "$item[0] " }
		asp: G A pyr { print "$item[0] " }
		glu: G A pur { print "$item[0] " }
		ala: G C base { print "$item[0] " }
		gly: G G base { print "$item[0] " }
		val: G U base { print "$item[0] " }
		tyr: U A pyr { print "$item[0] " }
		trp: U G G { print "$item[0] " }
		cys: U G pyr { print "$item[0] " }
		phe: U U pyr { print "$item[0] " }
		leu: U U pur | C U base { print "$item[0] " }
		
		amber: U A G { print "$item[0] " }
		ochre: U A A { print "$item[0] " }
		opal: U G A { print "$item[0] " }

		base: pyr | pur		
		pyr: U | C
		pur: G | A
	
		U: /U/i
		A: /A/i
		G: /G/i
		C: /C/i
			
GRAMMAR

my $p = new Parse::RecDescent( $grammar ) or die "Compile error\n";


while ( <DATA> )
{
	print;
	chomp;
	unless ( defined $p->seq( $_ ) )
	{
		print "\nOoops\n";
	}
}

__DATA__
AUG AAA GGC AGA AAG UAA