| Code | Meaning |
|---|---|
| \w | Alphanumeric Character |
| \W | Non-Alphanumeric Characters |
| \s | White Space |
| \S | Non-White Space |
| \d | Digits |
| \D | Non-Digits |
| \b | Word Boundary |
| \B | Non-Word Boundary |
| \A or caret | At the Beginning of a String |
| \Z or $ | At the End of a String |
| . | Match Any Single Character |
| Code | Meaning |
|---|---|
| * | Zero or More Occurrences |
| ? | Zero or One Occurrence |
| + | One or More Occurrences |
| { N } | Exactly N Occurrences |
| { N,M } | Between N and M Occurrences |
| .* <thingy> | Greedy Match, up to the last thingy |
| .*? <thingy> | Non-Greedy Match, up to the first thingy |
| [ set_of_things ] | Match Any Item in the Set |
| [ caret set_of_things ] | Does Not Match Anything in the Set |
| ( some_expression ) | Tag an Expression |
| $1..$N | Tagged Expressions used in Substitutions |