Awesome! Check this out:

Hit form loop on form:1
Hit inputfield loop
submitting request to form:1
Hit form loop on form:2
Hit inputfield loop
submitting request to form:2
Hit form loop on form:3
Hit inputfield loop
matched firstname regex
submitting request to form:3
Hit form loop on form:4
Hit inputfield loop
submitting request to form:4
[download]

It's working with the first form, and then I'm using mech->back because it navigated away from the page, as you suggested (nice catch). Any tips on how to iterate through subsequent forms after performing mech->back?