In the control panel, under users, check the list. If any (or all) say "shell" as the type, you're set. If you're on Windows, go to Start...then Run. Type 'telnet yourdomain.com' (without the quotes and substituting your domain name of course.) Alternately you could type telnet zuul.dreamhost.com (or whatever your 'machine' name is. Thats under 'machine' on the user list.)
Then type pwd and press enter.
That tells you where you're at.
Type cd plus domain name.
That moves you there. Example cd pics-by-jim.com
If its in a folder, you could do another cd foldername or simply in one command cd pics-by-jim.com/myperlscriptsarehere
ls -la will list the files in the directory where you are.
chmod 755 perlname.pl (where perlname.pl is filename) will make the ls -la out beside that filename look like so...
In the case of a script you want Owner (read, write, execute), Group (read and execute), Other (or 'World'), (read and execute). That translates to chmod 755 perlscriptname.pl
(You wouldn't want the "group" or the "world" to write to your file. They could then modify your script. That would be a bad thing.) But they need to read and run it.
Don't care to use the shell?
Most (all?) ftp programs offer a way to do this. I use WS-FTP. Once you get logged in via ftp, browse out to the perl script (or whatever file) you want to change permissions on.
Single left click on the filename to highlight it. Then right click, select chmod (UNIX) and check the appropriate boxes.
There's tons of info on the web explaining all this stuff...better than I can. If you use the shell...type man chmod for instance for more info. But do some unix chmod etc in your favorite search engine for tons of stuff.
(If I don't reply for a while Ohio is getting a huge ice storm and power is out more than its on.)