in reply to debugging - straw poll ...

Definitely print / printf!   A couple of tricks I've used over the years, both in C and Perl:
  1. Put something in the print statement to indicate it's temporary.  I use 'TFD' ('Temporary For Debugging'), which is easy for me to search for after I'm through debugging, to take out all of the lines containing it: 
      print "TFD>  About to call &parse_results ...\n";
  &parse_results($p);
  printf "TFD>  Done &parse_results, p->[0] = '%s'\n", $p->[0];

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  2. Put reverse-video escape sequences around text to really make it stand out. "<ESC>[7m" will turn ON reverse-video for ansi-capable terminal windows (eg. *nix), and "<ESC>[m" will turn if OFF (this will especially be helpful when you're generating tons of output, as the eyes can quickly spot reverse-video text): 
      if ($mystr =~ /Total lines processed:\s+(\d+)/) {
      my $total = $1;
      return $total;
  }
  print "TFD> \e[7mUnexpected format of 'mystr':\e[m\n";
  print "TFD>     '$mystr'\n";

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