The qw operator will see those arrays as a single element each. seperate with white space. You don't want a nested loop, you want to look at both arrays in a single loop over an index. I'll assume they are the same length.

my $x = 1;
my $y = 2;
my @a = qw(1 2 3);
my @b = qw(7 8 9);
for (0 .. $#a) {
    print "$x:$a[$_] $y: $b[$_]\n";
}
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