perldoc -f MessageBox();
No documentation for perl function `MessageBox();' found
[download]

You'll need to give us a little more code, since "MessageBox" is NOT a Perl function.

Is it a sub? JavaScript? a shot-in-the-dark to see just how well Perl DWIMs?

Update: ikegami's note is probably right on target: IMPE (painful experience!), Excel versions prior to 2010 behave exactly as he surmises... and I'd be surprised if M$ has changed that in more recent versions. So, definitely, "run the executable directly"!