2
0
a

##</code><code>##

input
a

##</code><code>##

use Parse::RecDescent;

my $text = "input [2:0] a";

my $grammar = q {
	rule : 'input' range(?) identifier 
		{
			print $item[1]."\n";
			if (defined @{$item{range}->[0]}) {
				my @arr = @{$item{range}->[0]};
				foreach my $i (@arr) {
					print $i."\n";
				}
			}
			print $item{identifier};
		}
	range : "[" from_num ":" to_num "]" {$return = [$item{from_num}, $item{to_num}]}
	from_num : number {$return = $item{number}}
	to_num : number {$return = $item{number}}
	number : /[0-9][0-9_]*/ 
	identifier : /[a-zA-Z][a-zA-Z_0-9\.]*/
};

my $parser = new Parse::RecDescent($grammar) or die "Bad Grammar";

$parser->rule($text);