for my (...) is experimental at <...>
# With 'undef's:
Use of uninitialized value <...>
Use of uninitialized value <...>
[1-2-3][abc-zz-79][444--]
Use of uninitialized value <...>
Use of uninitialized value <...>
[1-2-3][abc-zz-79][444--]
Without 'undef's -- no stepping out of an array:
[1-2-3][abc-zz-79]
[1-2-3][abc-zz-79]