iMacros help

I was working on a macro to guess this particular code:
CowBoyBeebopXvj5ks21o73kdp4if9md5jp47???? (number, letter, letter, number)

The macro is done in imacro.
For my macro I have a file in datasources folder called input.txt. It has a copy of every possible combination, like this:
[iOpus]
name0=0
name1=0aa0
name2=0ab0
name3=0ac0

My code is:
SET !DATASOURCE input.txt
SET !VAR1 CowBoyBeebopXvj5ks21o73kdp4if9md5jp47{{name!LOOP}}
TAG POS=1 TYPE=INPUT:TEXT FORM=NAME:regf ATTR=ID:register_username CONTENT={{!VAR1}}
TAG POS=1 TYPE=INPUT:SUBMIT FORM=ID:regf ATTR=NAME:Submit&&VALUE:I<SP>agree<SP>-<SP>continue<SP>sign<SP>
;up
wait seconds=1

However the string it actually inputs is: CowBoyBeebopXvj5ks21o73kdp4if9md5jp47__undefined__

Question is:  How do I get it to put out the string as you may have guessed I want it being output like?

>>13
Firefox...

Thank you for this enlightenment.  Can you link me to where it says it is IE only?

Something like this is not something I'd usually address and wouldn't know to check if it was compatible with firefox when the add on is for firefox.

I'll go and install it in IE and check how the script works then.