use strict;
use warnings;
use MCE::Shared;

my $string = MCE::Shared->scalar("First value");

sub do_subroutine
{
    print "I am the subroutine and my PID is $$\n";
    $string->set("Second value");
}

print "I am the invoking process and my PID is $$\n";
print "The value of \$string is ", $string->get(), "\n";

unless (fork)
{
    do_subroutine ();
    exit;
}

my $waited_pid = wait;

print "The PID of the child upon whom I waited was $waited_pid\n";
print "The value of \$string is ", $string->get(), "\n";

__END__

I am the invoking process and my PID is 22725
The value of $string is First value
I am the subroutine and my PID is 22727
The PID of the child upon whom I waited was 22727
The value of $string is Second value