[ic] [charge] tag usage questions

[Postfix User]

Hi -

I'm looking for some assistance using $Tag->charge() for a global
UserTag that I am writing.

The documentation on the IC site is pretty sparse and the code, while
readible does leave a few questions.

I understand that the first parameter is $charge_type (e.g. the
payment module name/type -- authorizenet, boa, etc), however, I dont
understand what the second parameter $opt requires for data.

>From what I can see in the source for charge(), $opt is a hash that is
passed in.

What are the required keys for this hash?

I appreciate your assistance!

Thanks!