You need to return two array references from the subroutine.

use strict;
use warnings;

my ($ref_to_a, $ref_to_b) = getlists();
print qq{@$ref_to_a\n@$ref_to_b\n};

sub getlists {
    my @foo = (1,2,3);
    my @bar = (4,5,6);
    return \@foo, \@bar;
}
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BTW, interpolating an array inside double quotes will, by default, space-separate the elements; you don't need the join.

Cheers,

JohnGG