Well, in that case, you might be better off with the pairwise function of List::MoreUtils:

$ perl -Mstrict -Mwarnings -E '
    use List::MoreUtils qw{pairwise};
    my @x = 0 .. 3;
    my @y = map { 10 + $_ } @x;
    say for pairwise {
        "$a + $b = " . ($a + $b) . "; $b - $a = " . ($b - $a)
    } @x, @y;
'
0 + 10 = 10; 10 - 0 = 10
1 + 11 = 12; 11 - 1 = 10
2 + 12 = 14; 12 - 2 = 10
3 + 13 = 16; 13 - 3 = 10
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Note how $a holds @x elements and $b holds @y elements. These ($a & $b) are the same special variables used by sort, so don't declare them; they're described in perlvar - SPECIAL VARIABLES - General Variables. You can use them in either order: cf. $a + $b and $b - $a.