Why not just:

while(@arr) {
    my ($x,$y) = (shift(@arr), shift(@arr));
    ...
    }
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Update: ... looks [like] the each generator ...
Maybe (see List::MoreUtils):

use List::MoreUtils qw(natatime);
;;
my $it = natatime 2, @arr;
while (my ($x, $y) = $it->()) {
    ...
    }
[download]