in reply to From PHP to Perl - Should I, and how?
Yes, you should learn Perl, for the same reason you should add any language to your toolkit. It gets easier to clearly express your intent in code as you learn the idioms common across different languages. You also get an idea for what concepts are easier to express in a particular language, which will give you whole new ideas for how to organize a project. I initially learned Perl because of how much easier it was to express regular expressions compared to PHP, and those regular expressions changed how I looked at text manipulation for a very long time indeed. Once I got the hang for coding in Perl, everything including GUI and Web development became much easier and definitely more powerful for me than in PHP. Your mileage may vary, of course.
You don't lose anything by using Perl instead of PHP, but fewer libraries are effectively built-in to the language. Database handling and a bewildering assortment of Web-specific features are available via external libraries on CPAN.
Now on to your specific questions:
Go ahead and learn Perl. It's always worth your time to expand your knowledge.