I've often seen code that, although it doesn't care about the exact number of replacements, it cares about whether a replacement was made (the number would be 0 or 1 since it's not a global replacement). This is typically used for tokenizing by deleting the tokens from a string (note: this might not very efficient for long strings!). The following is a simple example for tokenizing a space-delimited list of numbers. 
$s = "213 3218 213";
while ($s =~ s/^(\d+)\s*//) {
  print "$1\n";
}
if (length $s) {
  print "Error! didn't expect this: '$s'\n";
}

[download]

This contrived example could probably be done more simply in other ways, but for more complicated tokenizers it is not such a bad approach.

In reply to Re^4: Stupid mistakes I repeatedly make by itub
in thread Stupid mistakes I repeatedly make by brian_d_foy

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