my $valid_POSIX = qr{
  alpha | alnum | ascii | cntrl | digit | graph |
  lower | print | punct | space | upper | word | xdigit
}x;
 
... 
 
my %macros = (
  # utf8/POSIX macros
  alpha => 'letters',
  alnum => 'letters and digits',
  ascii => 'all ASCII characters (\000 - \177)',
  cntrl => 'control characters (those with ASCII values less than 32)',
  digit => 'digits (like \d)',
  graph => 'alphanumeric and punctuation characters',
  lower => 'lowercase letters',
  print => 'alphanumeric, punctuation, and whitespace characters',
  punct => 'punctuation characters',
  space => 'whitespace characters (like \s)',
  upper => 'uppercase letters',
  word => 'alphanumeric and underscore characters (like \w)',
  xdigit => 'hexadecimal digits (a-f, A-F, 0-9)',
);