Note: I found a bug in my earlier answer, since I can't edit it, I am posting this follow up. If the string to replace has the substring you are trying to find, it can get into an endless loop. Here is an updated ansewer:

  my $string  = '01234567890';
  my $find    = '0';
  my $replace = 'a';  

  my $pos = index($string, $find);

  while($pos > -1) {
    substr($string, $pos, length($find), $replace);
    $pos = index($string, $find, $pos + length($replace));
  }

[download]

In this case, an s/// regex is actually 5% faster.

In reply to (dkubb) Re: (3) Answer: How do I replace a substring (if exists) with a different substring in a string? by dkubb
in thread How do I replace a substring (if exists) with a different substring in a string? by kommesel

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