Multi-step primers with the !PREVIOUS_RESPONSE_FORM token

Sometimes, you need to fill out forms generated by the previous primer. The first page's form could ask for the user, and submitting that could lead to a second page showing a SECOND form, asking for the password.

The special Custom Primer URL token !PREVIOUS_RESPONSE_FORM will use the form in the previous primer's response, fill out the variables specified in Custom Primer Variables, and submit that.