As I was next to you in today's Raku gathering, I came up with this as a
sort-of answer. Not very happy with it but it gets partway there.
#!/usr/bin/env perl6
use v6.d;
## Simple version to check membership, but the type error won't tell which
strings
# subset Critter of Str where any
## This
I was just playing around with using a "subset" to restrict a
string to a set of allowed values:
subset Monster of Str where * eq any( << godzilla mothera blob
tingler grendel minotaur >> );
my Monster $thingie;
$thingie = 'grendel'; # accepts this as expected
$thingie = 'nada'; # f
