Could a colon perforation be confused with a anal fissure? how can i tell the difference? worried i might get peritonitis if i have a perforation.

No it shouldn't : anal fissure will usually give you pain in the anal area and mostly after bowel movement. Colon perforation is a life threatening emergency presenting with severe abdominal pain, nausea, fever and usually progressing to more severe symptoms of not addressed promptly. Recommend to see your general surgeon or gastroenterologist if you having rectal pain.