use strict;
use warnings;

for (1..5) {
  my $string = q{It's a cat and mouse game.};

  my $i = length($string) + 1;
  CHAR: while ($i--) {
    for my $c (substr($string, $i, 1)) {
      next CHAR unless $c =~ /^[a-zA-ZäöüßÄÖÜ]$/;
      # do whatever you want here
      $c .= $c x rand(7);
    }
  }

  print $string, "\n";
}