Tried your code snippet and it works fine. Maybe there's something wrong with one of your event subs? Or your general installation? What windows, perl (perl -v) and GUI (ppm query) versions are you using? Check your own code in a script that does nothing else (see below) and see if it does the same kind of misbehavior.
use Win32::GUI; $Window = new Win32::GUI::Window ( -name => 'Main', -text => 'Test', -pos => [100, 100], -size => [320, 240], ); sub Main_Terminate {-1}; @Data = (17..42); my $DataList = $Window->AddCombobox( -name => 'DataList' ,-width => 70 ,-height => 100 ,-top => 5 ,-left => 70 ,-addstyle => WS_VSCROLL | 2 ); my $key; foreach $key ( @Data ) { $DataList->Add( $key ); } $Window->Show (); Win32::GUI::Dialog ();