in reply to Re: Homework question list
in thread Homework question list

2. Compare two arrays and show the elements that exist in both (I actually screwed up in my live question, but the answers were still informative). This is a great question because it shows how someone thinks. Lower level devs use nested loops (I did, when this was thrown at me a few years ago). Smart people use hash slices. Really smart people use 'undef'd hash slices to save memory.
Could you give an example of the "hash slice" method? Using hashes is a good way (something like my %temp; my @doubles = grep { ++$temp{$_} == 2 } @a1, @a2; works nicely), but I can't seem to figure out the "(undef'd) hash slice" method. Please enlighten me :-)