If the perl version is 5.2 change it to 5.20

For consistency, now that perl 5.20 is supported, handle the special
case of version "5.2" in the same way that "5.1" was handled previously
(3f71aa3707a10ee214489520e96fef87fbaf7109)

Note: this was pointed out to me by @haarg
Split perl version logic into if/else block - #279

Split the special perl logic/handling for 5.1/5.10 and 5.2/5.20 into a
multi-line if/elsif/else block for better readability.

(this was requested by @joshk)
Additional stylistic changes (remove 'return' calls) - #279

Removed return statements in the new perl 5.1/5.10 and 5.2/5.20
version handling, as requested

@joshk - thanks for the feedback and giving me the chance to update to
follow your style guidlines. As you can probably guess, I don't write in
ruby too much :)
Merge pull request #279 from vanstyn/master

If the perl version is 5.2 change it to 5.20