#!/usr/bin/perl
use strict;
use warnings;
use Time::Local;
use Time::HiRes qw[ time ];
use POSIX ":sys_wait_h";

my $ReturnValue = 0;

sub MainSub()
{
my $Sub = "MainSub";
my $SubReturnValue = 0;

my $CommandLine;
my $Command = qq(echo 'Hallo, sleeping for 120 seconds ...'; sleep 120 2>&1);
open (COMMAND, '-|', "$Command");
while (<COMMAND>) {
	eval {
		local $SIG{ALRM} = sub { die("TimerTriggerStatus\n"); };
		alarm(10);
		printf "%s : %s\n", scalar localtime(), "$Sub - timer set to 10 seconds";
		
		chomp;
		$CommandLine = $_;
		printf "%s : %s\n", scalar localtime(), "$Sub - CommandLine received:\n$CommandLine";
	};

	if ( $@ eq "TimerTriggerStatus\n" ) {
		printf "%s : %s\n", scalar localtime(), "$Sub - timer triggered";
		&TimerHandler;
	};
}
close (COMMAND);

return ($SubReturnValue);
} # end of sub MainSub


sub TimerHandler() {
my $Sub = "TimerHandler";
my $SubReturnValue = 0;

printf "%s : %s\n", scalar localtime(), "$Sub - timer expired";

alarm(10);
printf "%s : %s\n", scalar localtime(), "$Sub - timer set to 10 seconds";

return ($SubReturnValue);

} # end of sub TimerHandler


sub TimerSub() {
my $Sub = "TimerSub";
my $SubReturnValue = 0;

printf "%s : %s\n", scalar localtime(), "$Sub - run after timer interrupt";

alarm(10);
printf "%s : %s\n", scalar localtime(), "$Sub - timer set to 10 seconds";

return ($SubReturnValue);

} # end of sub TimerSub

#### MAIN ####
printf "%s : %s\n", scalar localtime(), "BEGIN - MAIN";
($ReturnValue) = &MainSub;
printf "%s : %s\n", scalar localtime(), "END - MAIN";

##</code><code>##

# time ./TestSigalrm.pl
Wed Jul 24 08:38:20 2019 : BEGIN - MAIN
Wed Jul 24 08:38:20 2019 : MainSub - timer set to 10 seconds
Wed Jul 24 08:38:20 2019 : MainSub - CommandLine received:
Hallo, sleeping for 120 seconds ...
Alarm clock

real    0m10.018s
user    0m0.014s
sys     0m0.002s