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All the Perl that's Practical to Extract and Report

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  • If you use
    $pos = index($str, '%');
    everywhere, if your result was a "%" character, you would end up doubly decoding it. You should be using the position of the next occurence of "%" substring, thus, continue from after the previous value of $pos, instead of starting again from the start of the string.

    I have no idea if substr() in this ancient version of the language could actually handle that.

  • sub ue {
        $str = $_[0];
        while ($str =~ /%(\w\w)/) {
            $s = sprintf('%c', hex($1));
            $str =~ s/%\w\w/$s/;
    Tested with:
    print do ue("%41%20%42%20%43");
    print "\n";
    Works in perl 1.0_15 and perl 5.8.0 :)
    • To deal with the problem that bart describes, you need to re-build the string entirely.

      sub ue {
          $in = $_[0]; $out = '';
          while ($in =~ s/%(\w\w)|([^%]+)//) {
              $out .= ($1 ? sprintf('%c', hex($1)) : $2);
              $1 = $2 = '';

      Tested with:

      print do ue("%41%2541%20%42%20%43");
      print "\n";

      No longer works with recent Perls, because those don't allow clearing $n manually. In Perl 1, you had to, because otherw