docs: def unary_set_expr(self, ctx, oper, postoper=False):
          """
          Returns the MUF needed to do an unary operation on the lvalue. (++, --.)
          """
          if self.readonly:
              raise MuvError(
                  "Cannot increment or decrement constant '%s'." % self.varname,
                  position=self.position
              )
          varname = ctx.lookup_variable(self.varname)
          if varname is None:
              raise MuvError(
                  "Undeclared identifier '%s'." % self.varname,
                  position=self.position
              )
          if len(self.indexing) == 0:
              if postoper:
                  fmt = "{var} @ {var} {oper}"
              else:
                  fmt = "{var} dup {oper} @"
              return fmt.format(var=varname, oper=oper)
          if len(self.indexing) == 1:
              if ctx.target in ['fb7']:
                  if postoper:
                      fmt = (
                          "{idx} {var} @ "
                          "dup 3 pick [] "
                          "dup -4 rotate {oper} "
                          "swap rot ->[] pop"
                      )
                  else:
                      fmt = (
                          "{idx} {var} @ "
                          "dup 3 pick [] {oper} "
                          "dup -4 rotate "
                          "swap rot ->[] pop"
                      )
              else:
                  if postoper:
                      fmt = (
                          "{idx} {var} @ "
                          "dup 3 pick [] "
                          "dup -4 rotate {oper} "
                          "swap rot ->[] {var} !"
                      )
                  else:
                      fmt = (
                          "{idx} {var} @ "
                          "dup 3 pick [] {oper} "
                          "dup -4 rotate "
                          "swap rot ->[] {var} !"
                      )
              return fmt.format(
                  var=varname,
                  oper=oper,
                  idx=self.indexing[0].generate_code(ctx),
              )
          if ctx.target in ['fb7']:
              if postoper:
                  fmt = (
                      "{{ {idx} }}list {var} @ "
                      "dup 3 pick array_nested_get "
                      "dup -4 rotate {oper} "
                      "swap rot array_nested_set pop"
                  )
              else:
                  fmt = (
                      "{{ {idx} }}list {var} @ "
                      "dup 3 pick array_nested_get {oper} "
                      "dup -4 rotate "
                      "swap rot array_nested_set pop"
                  )
          else:
              if postoper:
                  fmt = (
                      "{{ {idx} }}list {var} @ "
                      "dup 3 pick array_nested_get "
                      "dup -4 rotate {oper} "
                      "swap rot array_nested_set {var} !"
                  )
              else:
                  fmt = (
                      "{{ {idx} }}list {var} @ "
                      "dup 3 pick array_nested_get {oper} "
                      "dup -4 rotate "
                      "swap rot array_nested_set {var} !"
                  )
          return fmt.format(
              var=varname,
              oper=oper,
              idx=" ".join(
                  x.generate_code(ctx)
                  for x in self.indexing
              )
          )