I too am wondering the same. Meanwhile, I tried executing the following line of code on shell, and it worked:

perl -e 'alarm shift @ARGV; exec @ARGV' 100 ./sh1.sh
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But I am not able to run this command from my perl script using the system function, within the while loop. That is weird! Any idea why this would happen? Also, the above command does not kill the process, it just suspends it. Is there a way to kill it?