sub zip {
    my ($ref1, $ref2) = @_;
    my @zip;
    while (@$ref1 || @$ref2) {
        push @zip => shift @$ref1 || undef;
        push @zip => shift @$ref2 || undef;
    }
    return @zip;
}

my $x = 1;
my $y = 2;

my @a=qw(1 2 3);
my @b=qw(7 8 9);

my @zip = zip(\@a, \@b);
while (my ($item, $element) = splice @zip => 0, 2) {
    print "$x: $item $y: $element\n";
}

##</code><code>##

for zip(@a,@b) -> $item, $element {
    say "$x: $item $y: $element";
}