POSIX Chacters Classes

The POSIX character class syntax, [:class:], is also available:

POSIX character class	Notes
alpha
alnum
ascii
blank	Equiv to C<[ \t]>, all horiz. whitespace
cntrl	Non printing control characters, e.g. newline and backspace
digit	\d
graph	Any alphanumeric or punctuation character
lower
print	Any alphanumeric or punctuation character or space
punct	Any punctuation character
space	\s
upper
word	\w
xdigit	Any hexadecimal digit: [0-9a-fA-F]

Example: "[01[:alpha:]%]" matches '0', '1', or an alphabetic character, or '%'.
Note: A perl extension allows any [:class:] to be negated by preceeding the
class name with a '^', e.g. "[:^digit:]" eq "\D".