I want to be able to use Perl to login to my Bank of America site to
grab my balance.

I am fairly competent in doing so on basic form posts, but looking at
their form site, they rely on multiple javascript files, and I'd
rather not go digging around in them.

Is there an easier way such as an application-for windows, firefox extension,
proxy service? that will let me see what kind
of communication is getting sent between the browser/page and the
server, that I can easily emulate?

IE, see all the variables that are sent, to which page, whether any
cookies are set, etc etc etc?

here is some information that may be of help to you.
All in all, I would still be wary of keeping my bank login details in
some perl script.  Let me know if this is what you were looking for

http://www.perl.com/lpt/a/2003/01/22/mechanize.html

http://66.249.93.104/search?q=cache:6NoA9xdU6osJ:www.perl-studio.com/buy-now/spider.php+Perl+automated+bank+login&hl=en&ct=clnk&cd=2