use Parse::RecDescent;
use Data::Dumper;
use strict;
use warnings;

$::RD_TRACE = 1;


my $grammar = q~

   expression: <leftop: term termop term> eod

   termop: /and/i | /xor/i | /or/i

   term: '(' <commit> expression ')' | condition

   condition: element comparison element

   element: '<' <commit> /-?\w+/ '>'
          | /\d+/

   comparison: /=[><]=/ <commit> <error: Unable to match comparison>
             | /=?[><]=?/
             | '='
             | '!='

   eod: /^\Z/

~;

my $parser = new Parse::RecDescent($grammar) or die;
#defined($parser->RecTest('h =>= h')) or die;

my $test = '(<MONTH> => <DAY>)'; # or (<MONTH> = <MARCH> and <DAY> = <TUESDAY>)';

print Dumper($parser->expression($test));