Just to make sure, %hoa2 is just another example? or is there a relationship between %hoa1 and %hoa2?

And to make sure aswell: you use elem[1] to refer to index 0? as in elem[1] = $array[0]?

Re-reading it helped a bit, but not quite as much as I hoped... this in particular confuses me:

Point 5: 'check if elem[1]-key1 = elem[2]-key2 ..etc until elem[last]-key2.'
Point 6: 'For checking elem[2]-key1 ..elem[last]-key2'

Point 5 says elem[1]-key1, point 6 says elem[2]-key1, is this correct? and what do you mean by ..etc, there are too many possibilities to continue comparing... (so please add another one)

And, any particular reason why you are sorting the elements in $HoA1{key1}? or is this done only to be able to compare it easily?

(This post has been updated several times, since I misread it first)