I started learning perl friday!!

I have one problem with this code... can someone tell me what is wrong here?

Code:
#!/usr/bin/perl

use strict;
use warnings;
 
sub bisplit {
	if(length($_)==2){
		my @lista = split($_[0],$_[1]);

		print (join(":",@lista)),"\n";
	}
}

bisplit(/\,/,"12,13,14,15,16");