... # your code above here
## Housekeeping

$workbook->close() or die "Error closing file: $!";

close(PROP);

{   ## COMPARISON
    use Data::Dump qw/dd dump/;
    my $old_ws_parse = $worksheet_parse;  # copy to new name for symmetry, below
    my $new_wb_parse = $parser->parse( 'new.xls' ) or die $parser->error(), "Error processing new workbook parse.\n";
    my $new_ws_parse = $new_wb_parse->worksheet( 'Sheet1' );
    open(my $compare_fh, '>', 'compare_formats.txt') or die "compare_formats.txt: $!";  # get in the habit of using lexical filehandles
    for my $row ( $row_min .. $row_max ) {
        for my $col ( $col_min .. $col_max ) {
            my $oldcell = $old_ws_parse->get_cell($row,$col) or next;
            my $newcell = $new_ws_parse->get_cell($row,$col) or next;
            # to STDERR
            dd 'oldformat => ', my $oldformat = $oldcell->get_format();  # you could use Data::Dump::dump() instead, if you want to print to your own file (similar to
            dd 'newformat => ', my $newformat = $newcell->get_format();
            # to file handle
            print $compare_fh 'oldformat => ', dump($oldformat), "\n";
            print $compare_fh 'newformat => ', dump($newformat), "\n";
        }
    }
}
exit;