I'm no CGI expert, but my intuition tells me that this is a bad idea. (Call it a case of "CGI code smell".)

But, FWIW, if the backtracking is to some form whose contents you control, I suppose that this form could pass (in a hidden field(s)) its identity and whatever extra information may be necessary to recreate it. Heck, I suppose it could pass its entire HTML (with allowances for the impossibility of infinite regress) as a quoted string in some mongo hidden text field...

I'm sure there are many problems with this approach. (E.g. what if the user wants to hit "back" twice? How much backtracking info will you burden each page with?)