#!/usr/bin/env perl
use warnings;
use strict;

print "[$$] Starting main program\n";

my @childs;
for my $count (1..3) {
    if ( my $pid = fork ) { # parent
        print "[$$] child pid is $pid\n";
        push @childs, $pid;
    }
    elsif ( defined $pid ) { # child
        sub1($count);
        exit 0;
    }
    else
        { die "[$$] couldn't fork: $!" }
}

for my $pid (@childs) {
    my $tmp = waitpid($pid, 0);
    print "[$$] done with pid $tmp\n";
}

print "[$$] End of main program\n";

sub sub1 {
    my $num = shift;
    print "[$$] started child process for $num\n";
    sleep $num;
    print "[$$] done with child process for $num\n";
    return $num;
}