the result of this inversion operation is a HoA  { key1 => [ value11, value12], key2 => [value21],  ...}

And neither

• a hash with key/value pairs { key1 =>value1 , key2 => value2, ...}
• a list with key/value pairs ( key1, value1, key2, value2 ,...)
• a list of arrays with pairs (tuples) ( [key1, value1], [key2,value2], ... )

IMHO all better interpretations.