You want to match alphabetic characters which include unicode
#!/usr/bin/env raku
use v6;
my $var = "\c[OGHAM LETTER RUIS]";
if $var ~~ /^<:letter>+$/ { # or just /^<:L>+$/ or even /^\w+$/
say "{$var} is purely alphabetic";
}
# vim: expandtab shiftwidth=4 ft=perl6