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use List::MoreUtils qw( all first_index indexes );

...

    return all { $l1->[$_] eq $l2->[$_ + $head_idx] } indexes @$l1;
}

sub in_list {
    my ($l1, $l2, $comp) = @_;
...
    # free!! *gasps*
    return all { $comp->($l1->[$_ + 1], $l2->[$_ + $head_idx]) } grep 
+{ $_ } indexes @$l1;
}