sub save {

    @types =
    (["Text files",           [qw/.txt .doc/]],
     ["All files",                '*'     ]);
    
    my $file = $mw->getSaveFile(
        -initialfile      => $save_file,
        -defaultextension => '.txt',
        -filetypes        => \@types);
    open OUTFILE, ">$file";
    print OUTFILE "whatever you want to save in that file";
    close OUTFILE;
    &exit;
}