note trizen A general solution: <code>my $nth = 4; my $str = 'a=>bb=>ccc=>dddd=>eeeee=>ffffff'; while ($str =~ /=>/g) { if (--$nth == 0) { substr($str, $-[0], $+[0] - $-[0], '~~|~~'); last; } } print "$str\n";</code> 1004836 1004836