Not simple dinky ones, but perhaps regexes that got you out of a bind, or were quite sneaky at what they did, ...

A couple of times recently I've used a "nested" regexp to pull off a bit of tricky substition. The "outer" regexp serves as a filter, and the "inner" regex, fired via /e, does a more targetted subsitution (or no substitution at all).

In the code below, the challenge was to turn words like "cowsCanFly" into "cows-can-fly".

$phrase = "NoMatch cowsCanFly sheepAreVeryCool NoMatch";

$phrase =~ s{
               \b
               (
                  [a-z]+
                  (?:[A-Z][a-z]+)+
               )
               \b
            }{
               my $word = $1;
               $word =~ s/([A-Z])/"-" . lc($1)/eg;
               $word;
            }gex;

print $phrase, "\n";
[download]

When I first posted this fragment (in this node), there was some concern that the regex engine wasn't reentrant, and that I'd just gotten lucky. Perhaps, though I've done this a few times with 5.6.0 or later, and haven't run into any problems.

japhy, since you're now a regex UberLord, perhaps you can vet this approach for reentrancy issues.

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