(mis)behaviour of getOpenFile

I am trying to use the getOpenFile widget (Mastering Perl/Tk page 568 -
First Edition).  Whilst this is perfectly OK when there are 3000 files
in a directory I do not get a list of files (even when leaving the
application running for a matter of minutes) to select from when there
are 6000 files in the directory.  Looking at the task manager I find
that Perl.exe is running and using about 70% of the CPU time and that
the memory used in lower than that available.  I can view the directory
using the Windows Explorer.  Is there a fundamental problem and/or how
can I make the widget work quicker?
 
Best regards
 
Henry Merryweather