opendir $dh, $dir_of_files or die "Couldn't open dir '$dir_of_files': $!";
my @comparefiles= readdir $dh;
closedir $dh;
for each $file in @comparefiles
{
  read_write_subroutine($file);
}

sub read_write_subroutine
{
put your whole code here which is currently you are using
}