[ic] Payment module questions

[Interchange user]

Hey there,

I'm working on a new payment module and have a couple questions (many more 
will follow, no doubt).

The payment gateway I'm using requires a credit card type (that is, 'VISA', 
'MASTERCARD' and so on). I've put the following chunk of code in 
checkout.html:

<SELECT NAME=mv_credit_card_type>
[calc]
my $accepted = $Variable->{CREDIT_CARDS_ACCEPTED};
my %cc;
my $out = "";
$cc{"Visa"} = "VISA" if $accepted =~ /visa/;
$cc{"MasterCard"} = "MASTERCARD" if $accepted =~ /mc/;
$cc{"Discover"} = "DISCOVER" if $accepted =~ /discover/;
$cc{"American Express"} = "AMEX" if $accepted =~ /amex/;
for (keys %cc) {
  $out .= "<OPTION VALUE=\"$cc{$_}\">$_";
}
return $out;
[/calc]
</SELECT>

Can I now access this variable using '$actual{mv_credit_card_type}' (assuming 
this hash was set up as in other payment modules)?

BTW, what's the best way to debug? Where does the '::logDebug()' function 
output to? How are payment modules called? Can you debug without having to 
place an order each time?

Secondly, can someone please give me specs on the return values that IC 
expects to receive in the %result hash? I can see more or less what's 
happening in other modules, but it's a little confusing.

Thanks in advance.