Please help: resource limit for running Perl under Apache?

Hi, I've a Perl script that does following:

-          Ssh to a device and get information, e.g.:  open(DEV, "/usr/bin/ssh -v statuser\@192.168.11.1 sh get client list| ");

-          Loop through the result and display as html.

The Perl script can complete without problem when run in bash or in Apache 2.2.

However, when I put it on a new Apache 2.4 server, the script can't display all output - the output table expected to be 1000 lines now ends at ~300.   Checked that it seems the ssh command terminated prematurely.  The "while (<DEV>)" loop exists as there is no more input data.   The Perl can also complete without problem when run in bash on the same server running Apache 2.4.

I wonder if there is any resource limit for CGI/Perl when running under Apache 2.4.   Default OS resource limit looks alright:

stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 15014
virtual memory          (kbytes, -v) unlimited

Sorry that I'm not web admin and don't have access to Apache logs.

Would anyone please help?   Thanks a lot.

Regards