$SIG{ALRM}=\&alrm_handler;

sub alrm_handler
{
   do...something here...
   sounds like die and cause shell
   command to be re-executed...
}

my $inLine;

while (alarm(20), $inLine = <> and $inLine !~ /^Done/)
{
    alarm(0);  # deactivate the alarm!!

    normal loop here...

}
print "Exiting\n";
exit;