Erm, IPC::Open3 is core (i.e. ships with perl) and has been for a while now (see perldoc perlmodlib). You shouldn't need to convince anyone to install it unless you've got a broked install of perl itself.

Update: Oh, and the alternative is to use 2>tmpfile and let the shell redirect stderr to a file. You then check if -s "tmpfile" and handle whatever error output if necessary.