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

pipe PREAD, CWRITE; # child -> parent

if (fork) {
    parent1();
}
else {
    child();
}


sub child {
    close PREAD; # child - close parent end of pipe

    print "child: start of proccess\n";
    syswrite CWRITE, "0\n";
    for (1..5) {print "child zZZZzzz\n";sleep 1;}
    print "child is awaking\n";
    syswrite CWRITE, "$_\n" for 1 .. 10;
    print "child ending\n";
    exit;
} # sub child


sub parent1 {
    close CWRITE; # parent - close child end of pipe

    chomp(my @erg = <PREAD>);
    print "parent got ", join(' - ', @erg), "\n";
    print "parent : ", (eof(PREAD)?'ENDE':'keine Ende'), "\n";
} # sub parent1


sub parent2 {
    close CWRITE; # parent - close child end of pipes

    my @erg;
    eval {
        $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
        alarm 2;
        chomp(@erg = <PREAD>);
        alarm 0;
    };
    if ($@) {
        die "other error : $@"
            unless $@ eq "alarm\n";   # propagate unexpected errors
        warn "parent : child got time out!\n";
    }
    else {
        alarm 0; # Ist das wirklich notwendig?
        print "parent got ", join(' - ', @erg), "\n";
        print "parent : ", (eof(PREAD)?'ENDE':'keine Ende'), "\n";
    }
} # sub parent2