while ( index($group, "!", $index) > -1 and $index<50000 ) {

##</code><code>##

use strict;
use warnings;


my $string = "abc!def!ghi!jkl!mno!pqr!stu!vwx!yz";
my $limit = 3;

$string = join("\n", split(/!/, $string, $limit));

print $string;