Character Meaning
^ Anchor for the beginning of a line
$ Anchor for the end of a line
\A Anchor for the start of a string
\Z Anchor for the end of a string
. Any character
\w Any letter, digit, or underscore
\W Anything that \w doesn't match
\d Any digit
\D Anything that \D doesn't match (non-digits)
\s Whitespace (spaces, tabs, newlines, and so on)
\S Non-whitespace (any visible character)