I am new to Perl. I would like to know if Perl has RIA (Rich Internet Application) frameworks like zkoss or Vaadin or GWT from Java?
How do Java and Perl compare in terms of memory management and pattern design?
In short, no. But take a look at the Catalyst Framework. But no, I don't know anything as glossy and point&click-y as "zkoss" or "vaadin". HTML+CSS+Perl works fine as well, if you know them.
Perl is a garbage collected. Variables that are no longer referenced get freed. Beware that in general, Perl tends to prefer time efficiency over memory efficiency what does not mean that perl is in any way bloated. Also beware, that circular references have to be manually broken, or the garbage collector won't be able to detect those variables to be collected. That is somewhat unlike Java.
Yes, of course you can use any patterns you like. Perl doesn't make objetc orientation too easy by default, however the Moose Framework helps with that. Whith Perl, you can also use some functional patterns like closures or currying that are not available, or not as easily available, in Java. Note that Anonymous Classes get really hard to create with Perl, but hard things are still possible. You often don't need them anyway with closures.
See the info page of the "perl" tag on SO: https://stackoverflow.com/tags/perl/info especially the free books section. I like Higher Order Perl, although reading through the basics first should be sensible.
The Perl documentation with perltoot, perlboot and other pages has good introductions to traditional Perl object orientation techniques, which differ superficially from the Moose interface.