To expand on this great suggestion from Bloodnok, I found a nice tutorial for the parser.

http://www.perl.com/pub/2001/06/13/recdecent.html

From

http://www.perlmonks.org/?node_id=108182

Sample code from the tutorial.

use strict;
use warnings;
use Parse::RecDescent;

# Create and compile the source file

my $parser = Parse::RecDescent->new
    (
        q(
            startrule : day  month /\d+/
            day : "Sat" | "Sun" | "Mon" | "Tue" | "Wed" | "Thu" | "Fri
+"
            month : "Jan" | "Feb" | "Mar" | "Apr" | "May" | "Jun" |
                    "Jul" | "Aug" | "Sep" | "Oct" | "Nov" | "Dec"
          )
      );


# Test it on sample data
print "Valid date\n" if $parser->startrule("Thu Mar 31");
print "Invalid date\n" unless $parser->startrule("Jun 31 2000");
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