```{index} single: is_universal (mro) ``` ```{index} single: mro::is_universal ``` # is_universal Report whether `$class` is `UNIVERSAL` itself or one of its ancestors via `@ISA`. ## Synopsis ```perl if (mro::is_universal($class)) { ... } ``` Returns a true value exactly when every class in the program can inherit methods from `$class`. That happens in two cases: the class literally *is* `UNIVERSAL`, or something has pushed it into `@UNIVERSAL::ISA` (directly or indirectly). Most programs never see the second case, but frameworks that mix a trait into `UNIVERSAL` rely on it. A single argument is required; calling with any other arity croaks with `Usage: mro::is_universal(classname)`.