Comment 3 for bug 991650

The author of Params::Classify acknowledges here:

http://www.perlmonks.org/?node_id=886909

... that the module is not thread-safe, which causes segfaults and/or 100% CPU utilization when used with libapache2-mod-perl2 and apache2-mpm-worker.

Also:
https://rt.cpan.org/Public/Bug/Display.html?id=74222
https://rt.cpan.org/Public/Bug/Display.html?id=72743
http://stackoverflow.com/questions/13054360/mod-perl-script-going-in-to-a-tight-loop-during-use-processing
http://stackoverflow.com/questions/10427227/apache-children-hanging-mod-perl/