Regexp (RE) with Fork, or threads, are safer now! In Perl 5.6.1 I was trying to use the fork emulation, but my app crash on some RE. But I was testing the same app with Perl v5.8 and works fine.

Perl 5.8 comes with threads (ithreads) turn on by default, and RE is used in Perl all the time. They wont put threads on if this is not safe!