my $child_pid = open my $child_fh, '-|';
if ( ! defined $child_pid ) {
    die "Can't fork: $!";
}
if ( $child_pid ) {
    # parent
    my $child_says = do{ local $/; <$child_fh> };
    close $child_fh;
}
else {
    # child
    # ... process your heart out ...
    print "my result";
}