$ perl -MCarp=verbose a.pl
open3: close(4) failed: Bad file descriptor at /usr/share/perl/5.8/IPC/Open3.pm line 70
        IPC::Open3::xclose(4) called at /usr/share/perl/5.8/IPC/Open3.pm line 218
        IPC::Open3::_open3('open3', 'main', '<&4', '>&STDOUT', '>&STDERR', '/bin/cat') called at /usr/share/perl/5.8/IPC/Open3.pm line 229
        IPC::Open3::open3('<&4', '>&STDOUT', '>&STDERR', '/bin/cat') called at a.pl line 21