Re^4: Stupid mistakes I repeatedly make

[itub]

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";
}

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

[Tanktalus]

I stand corrected. Thanks, itub and Roy Johnson. Normally I do this in two phases (the match, then the substitution), but that's just me, and not something to advocate as the One True Perl Way. :-) I just find it makes more sense, but largely because I forget about s returning the number of matches, which is largely due to lack of need (usually I do the substitution and continue without any branching on whether it was succesful or not).