It's been quite some time since I've written anything dealing with alarm but something like this may do what you need

$SIG{ALRM} = sub {
   #cleanup lockfile
   #cleanup anything else
   exit;
}

alarm(1200);
# do stuff
# If you have system calls here (i.e. sysread) you
# may need to do some wrapping with eval etc.  (as per
# the alarm perldoc
alarm(0);
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This is untested. I think the approach will work, but as always, you mileage may vary. Update: time is in seconds not minutes.