The way which I handled this within CGI::Upload was to make use of File::Basename and HTTP::BrowserDetect. For example:

use File::Basename;
use HTTP::BrowserDetect;

fileparse_set_fstype(
    do {
        my $browser = HTTP::BrowserDetect->new;
        return 'MSWin32' if $browser->windows;
        return 'MacOS' if $browser->mac;
        $^O;
    }
);
my @file = basename($path, '\.[^\.]*');
[download]

This code makes use of HTTP::BrowserDetect to determine the browser and thus operating system which has submitted the multipart-encoded request. This is then used to set the file-system parsing routines of File::Basename appropriately - The basename method of this module is then used to strip the directory path and return the submitted file name.