code: def match_var(self, tokens, item):
          
          setvar, = tokens
          if setvar != wildcard:
              if setvar in self.names:
                  self.add_check(self.names[setvar] + " == " + item)
              else:
                  self.add_def(setvar + " = " + item)
                  self.names[setvar] = item
docs: Matches a variable.