sub my_lc_warn {
  not defined wantarray and warnings::warnif("void", "my_lc used in void context");
  unless (wantarray) {
     @_>1 and warnings::warnif("my_lc called in scalar context with extra arguments (".join(",",@_).")");
     return lc shift;
  } else {
     return map lc $_,@_;
  }
}