Select Code to Download

qr{\A[A-Za-z0-9](?:[A-Za-z0-9_.-]*?[A-Za-z0-9]|)\z}

$ perl -E '
    my @x = (qw{A AA AAA _ __ ___ -A A- A.A A. .A A-A A_A}, "A\n", "A\
+tA");
...
|A
| is BAD
|A      A| is BAD