Fix bug of mal-structured dup group - When a user changes tween type of a tween, the structure of dup group may not satisfy the requirement of new type. - It causes unexpected behavior. - It is fixed by checking structure and remove mal-structured ones.

divert([-1])

define([_arg1], [$1])

define([_foreach], [ifelse([$2], [()], [],
[define([$1], _arg1$2)$3[]_foreach([$1], (shift$2), [$3])])])

define([foreach], [pushdef([$1])_foreach($@)popdef([$1])])

divert[]dnl