corn snake
How often have you been attempting feeding? Time is needed in between attempts (7-10days) to allow the stomach to recover. Continued regurg. is the result if this step is skipped.
As always, re-evaluate your husbandry. Most common causes for regurgitation are too cool temps and stress although other things can cause it too.
If this snake looks like it's going to die, a vet visit seems in order eh?
ball python
How long has this been apparent? My first impression is that it is one of two things... an individual anomoly or dehydration. If the problem is new, or getting worse, than it probably isn't normal and is worth more attention. Is this snake otherwise examined fine? Does it appear dehydrated? Are mites present? Shedding normal? Bloodwork might be my first diagnostic if still searching for a cause. X-ray, ultrasound, CAT and/or MRI are all methods of looking into the head. Different clinics will have access to a variety of these.
Good luck 
Ian