use Types::Standard qw(ArrayRef Int);
   
   BEGIN {
      my $type = ArrayRef->of(Int);
      *is_ArrayRef_of_Int     = $type->compiled_check;
      *assert_ArrayRef_of_Int = \&{ $type };
      *to_ArrayRef_of_Int     = sub { $type->coerce(@_) };
   }
   
   if (is_ArrayRef_of_Int($var)) {
      ...;
   }