[ic] Quick and dirty "write to file"

[Peter N]

And a followup question: I have the following code snippet:

[if cgi add_to_list]
 [log file="email_list.txt" type="text" interpolate=1]
  [cgi email]
 [/log]
[/if]

Where do I need to place this code so that it is invoked on checkout?
I tried putting it on receipt.html, but nothing is written to the log,
presumably because my form variable, add_to_list, is not being passed
from checkout.html.

Thank you again,

Peter