print mine ("Terence and Philip are sweet", 'c', 'Z', 3);

##</code><code>##

sub crep {
  my ($str, $chr, $rep, $nth) = @_;
  my $pos = 0;
  while (--$nth > 0) {
    $pos = index $str, $chr, $pos;
    last if $pos < 0;
    $pos++;
  }
  substr ($str, $pos) =~ s/$chr/$rep/g if $pos >= 0;
  return $str;
}

##</code><code>##

sub crep {
  my ($str, $chr, $rep, $num) = @_;
  my $tstr = '';
  $tstr .= substr $str, 0, (1 + index $str, $chr), '' while --$num;
  $str =~ s/$chr/$rep/g;
  $tstr.$str;
}

##</code><code>##

sub crep {
  my ($str, $chr, $rep, $num) = @_;
  $str !~ /$chr/g and return $str while $num--;
  substr ($str, -1 + pos $str) =~ s/$chr/$rep/g;
  return $str;
}

##</code><code>##

sub crep {
  my ($str, $chr, $rep, $nth) = @_;
  my $pos = 0;
  ($pos = index $str, $chr, $pos)++ < 0 and return $str while --$nth;
  substr ($str, $pos) =~ s/$chr/$rep/g;
  return $str;
}