Security Hazard!
Are you sure you want to evaluate a user regexp?
The user can insert a (?{...}) construct
to include some Perl executable code, which can
in turn include a call to system, or
backticks, which can contain very bad things.
And there is more than one way to do nasty things.
The user can write a Denial-of-Service regexp,
a regexp which backtracks a lot and locks your machine.
See Mastering Regular Expressions page 140+
(the book with two owls on the cover)
Update
Yes, Perlplexer, you are right. The security hazards
are mostly irrelevant in a Perl/Tk program. Yet,
my warning still holds for any monk who would use
the answers in this thread for a CGI program (or
any client-server app for that matter).
