I need to get the folder names on my NAS (not the files inside).

First off, define "slow."

Secondly there are a lot of factors here that could affect your timing trying to do what you are doing. My immediate solution in Perl would be something along the lines of:

|
|  stuff before
opendir(DIR,"/some/path/where/the/folders/live") or die $!;
my @folders=();
while(my $entry = readdir(DIR)){
     next if ( $entry eq "." ) || ($entry eq ".." );
     next unless -d $entry;
     push @folders,$entry;
} 
|   rest of code 
# untested software, do not use to aim phaser banks.
[download]

But wait, if you are having performance issues using the "ls" command then we have to consider one or more of the following factors:

• Network latency issues to/from NAS
• NAS device architecture
• Filesystem type and efficiencies

It would seem to me that if "ls" is having an issue with performance acting on that collection of folders then anything you might use to emulate "ls" is going to have issues as well.

In my mind this is less of a Perl or scripting issue and more of a system issue.