Is encrypted code such as this script produces portable

Yes in so much as you script is portable

or are there any dependency issues?

No you can RTFS

Now the real question is does it offer any security from all but the most casual scriptkiddie.

No

How long would it take to decrypt a script XORed against 256 integer keys. A few seconds. A couple of minutes including writing the code. That would be if the script did not include the decoder with it! Change eval $prog to print $prog and it spews the source rather than runs.

See Also

source filters
Acme::Bleach
unbleach.pl
A real challenge

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print