# old loop code
    ########################################
    my $diff= easy( \@a, \@b );
    while(  @$diff  ) {
        my( $same, $aMin, $aMax, $bMin, $bMax )=
            splice @$diff, 0, 5;
        # ...
    }

    # new loop code
    ########################################
    my $diff= easy( \@a, \@b );
    my $same= 0;
    while(  @$diff  ) {
        my( $aMin, $bMin, $aMax, $bMax )= @$diff;
        # ...
        splice @$diff, 0, 2;
        # ...
    }
[download]

Ouch! Precisely what I wanted to avoid: a modification in the number of items. Well, you could export a constant for this number, whether it be 2 or 5.

BTW if memory efficiency is what you're worried about, why don't you just use 1 scalar for each item? After all, these are all just integers, so messing with pack()/unpack() or vec() would allow you to combine them, in one scalar. Only an 8 (or 20) byte string per item! The joy! The savings! (The pain!)