Also try:

use strict;
use warnings;

sub debuf{ select( ( select( $_[0] ), $|++ )[0] ) }

my ($child, $parent);
pipe($child, $parent) or die;

debuf( $parent );

my $pid = fork();
die "fork() failed: $!" unless defined $pid;
if ($pid) {
    close $child;
}
else {
    close $parent;
    print "child waiting\n";
    my $read;
    read($child, $read, 1);
    print "child exiting\n";
    exit(0);
}

print $parent "exit now\r\n\r";
print "parent going to wait\n";
waitpid($pid, 0);
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