Creating another process is (I think) the only way this is possible without creating a full-blown dialog or window--the messagebox API is inherently modal, methinks.

Here is the workaround code I came up with:

Main file:

use Win32::Process;

Win32::Process::Create($ProcessObj,
                       "C:\\perl\\bin\\perl.exe",
                       qq[perl -MWin32 -e "Win32::MsgBox('Test')"],
                       0,
                       NORMAL_PRIORITY_CLASS,
                       ".")|| die ErrorReport();

Win32::Process::Create($ProcessObj,
                       "C:\\perl\\bin\\perl.exe",
                       "perl messagebox.pl",
                       0,
                       NORMAL_PRIORITY_CLASS,
                       ".")|| die ErrorReport();

for (1..60) {
  print "$_\n";
  sleep(1);
}
[download]

And if you really want to know how to directly call the MessageBox API from Perl, here's messagebox.pl

use Win32::API::Prototype;   # von die infamous Dave Roth

ApiLink( 'user32.dll',
         'DWORD MessageBox( DWORD hwnd, LPTSTR lpText, LPTSTR lpCaptio
+n, DWORD wType)'
       ) || die;

$lpText = NewString("The text in the message box.");
$lpCaption = NewString("The Caption");

MessageBox(0,$lpText,$lpCaption,0);
[download]

--Solo

--
You said you wanted to be around when I made a mistake; well, this could be it, sweetheart.