use strict;

my $dir = "C:/some/dir";
my @files = glob("$dir/*.csv");

for my $file (@files) {
    print "Processing $file .....";
    my $ret_val = convert( $file );
    print ret_val == 0 ? "OK\n" : "Not OK Err: $ret_val\n";
}
print "Done!\n";

sub convert {
    my $file_to_convert = shift;
    # csv2xls code goes here
    # return 0 if conversion works OK
    # return error message if conversion fails
}