Look in archives. I think many people had problems with IPC::Open2 under mod_perl. So far the best solution I know is just replacing it with IPC::Run.
Seconded. Go with IPC::Run and you won't regret, since it works under mod_perl and gives you much more than the IPC::Open* family.
IPC::Run++
it's not just for system() anymore :) --Geoff
