enum Letter => 'a'..'z', 'A'..'Z';
enum Language => 'Perl 5', 'Perl 6', 'PASM', 'PIR'; # any others? ;)
-enum Metacharacter => '*', '+', '?', '.', '|', '(', ')', '[', ']', '\\';
+enum Metacharacter => ['*', '+', '?', '.', '|', '(', ')', '[', ']', '\\'];
my @valid_letters = ('a'..'z', 'A'..'Z');