X{1234}

##</code><code>##

\x{1234}      # \x{...}, not \X{...} or X{...}

##</code><code>##

/\X{1F00-1FE3}/

##</code><code>##

/[\x{1F00}-\x{1FE3}]/

##</code><code>##

utf8::encode($_[0]);

##</code><code>##

sub is_vowel {
    return $_[0] =~ /
        ^
        [\x{1F00}-\x{1FE3}\x{1FE6}-\x{1FFE}\x{0386}-\x{038F}\x{0390}\x{0391}\x{0395}\x{0397}\x{0399}\x{039F}\x{03A5}\x{03A9}\x{03AA}-\x{03B1}\x{03B5}\x{03B7}\x{03B9}\x{03BF}\x{03C5}\x{03C9}-\x{03CE}]
        \z
    /x;
}