#!/usr/bin/perl

my $command = "./program_to_run.pl";
my $fifo = "tmp.fifo";

system "mkfifo $fifo; $command >$fifo 2>&1 &";

open my $fh, "<", $fifo or die "Couldn't open fifo '$fifo': $!";
while (<$fh>) {
    print ": $_";
}
close $fh;
unlink $fifo;

##</code><code>##

#!/usr/bin/perl

my $pid = fork();
if ($pid) {
    exit;
} else {
    $| = 1;
    for (1..3) {
        print "foo";
        print STDERR "bar\n";
        sleep 1;
    }
    print "done.\n";
}

##</code><code>##

: foobar
: foobar
: foobar
: done.