| . | Any character (except newline) |
| (a|b) | a or b |
| (...) | Set "..." as Group |
| (?:...) | Set "..." as Passive Group |
| [xyz] | Range (matches x,y, or z) |
| [t-z] | Matches a letter t thru z |
| [0-9] | Matches digit 0 thru 9 |
| \x | Matches xth group (ie \2) |
| * | 0 or more of |
| + | 1 or more of |
| ? | 0 or 1 of |
| {3} | Exactly 3 of |
| {3,} | 3 or more of |
| {3,4,5} | 3,4,5 of |
| x? | Ungreedy modifier x (ie .?) |
| \w | Word |
| \W | Non-word/Symbol |
| \s | White space |
| \S | Non-white space |
| \d | digit |
| \D | Non-digit |
| \c | Control character |
| \O | Octal digit |
| ^ | [ | . |
| $ | { | * |
| ) | \ | + |
| ( | | | ? |
| > | < |
| [:upper:] | Upper case letters |
| [:lower:] | Lower case letters |
| [:alpha:] | All letters |
| [:alnum:] | Digits and letters |
| [:digit:] | Digits |
| [:xdigit:] | Hex Digits |
| [:punct:] | Punctuation |
| [:blank:] | Blank characters |
| [:xdigit:] | Hex Digits |
| [:space:] | Space and tab |
| [:cntrl:] | Control characters |
| [:print:] | Printed characters and spaces |
| [:word:] | Digits, letters and underscore |
| \n | Newline |
| \r | Carriage return |
| \t | Tab |
| \f | Form feed |
| \xhh | Hex character hh |