See my reply to bbfu above. You'd have to do something like:

sub adv_tr {
  my ($str, $x, $from, $to) = @_;
  my $pos = -1;
  ($pos = index($str, $from, $pos + 1)) == -1 and return $str while $x
+--;
  eval "substr(\$str, $pos) =~ tr/\Q$from\E/\Q$to\E/";
  $str;
}
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   MeowChow                                   
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