In the default template for the Confirmation Page I am using pretty URLs and
configured it such:

Billing Page -> checkout (with pretty URL /checkout
Comfirmation Page -> confirmation (with pretty URL /confirmation

When I initially begin the checkout process, I go to /checkout
When the form processes correctly I then go to /confirmation
Once there, if I click the "Edit" link or the Back link at the bottom, I return
to the checkout page but the url is no longer "/checkout" it is now
"index.php?mact=Orders..."

I was trying to see if I could correct this in the template.  It is using a
variable called $back_url.  I was unsuccessful.  I can simply set the template
to use "/checkout" as the link however, so that is a workaround.  Would there be
an appropriate template variable I am missing so if I change those settings in
the future the template will automatically pick it up?