| Pattern Element | Meaning |
|---|
| [a-fx] | Square brackets denote a character class. The pattern at left can match the letters a-f or x. Piraha has no pre-defined character classes and does not support the notions of unions or intersections insided character classes available in Java's regular expression package. |
| [^a-fx] | This is a negated character entity. It will match any character except a-f or x. |
| [^] | This pattern will match any character. |
| x{n,m} | The quantifier pattern will match the pattern x a minimum of n and a maximum of m times. |
| x{n,} | This version of the quantifier pattern will match n or more occurrences of x |
| x{,m} | This version of the quantifier pattern will match at most m occurrences of x |
| x+ | A shorthand for x{1,} |
| x* | A shorthand for x{0,} |
| x? | A shorthand for x{0,1} |
| \1 | Match the first backreference within this rule. Any of backreferences 1 to 9 may be matched by using \2, \3, etc. |
| {name} | Match the pattern named by name. Save the match in a backreference. |
| {-name} | Match the pattern named by name, but do not capture backreferences.| |
| (?=x) | Match the pattern x as a zero-width lookahead assertion |
| (?!x) | A negative zero-width lookahead assertion for pattern x |
| (x|y|z) | An ordered set of preferred ways to match. If pattern x does not succeed, try pattern y, and then z. There can be any number of alternatives in this set. |
| \b | A word boundary. A word is composed of letters, numbers, and the underscore. |
| $ | Match the end of the string. |
| ^ | Match the beginning of the string. |
| (?i:x) | Ignore case when matching x. |
| (?-i:x) | Do not ignore case when matching x.| |
| {OpenWhite} | A zero-width lookahead assertion that a new indentation level has opened, starting at the current position. |
| {CloseWhite} | A zero-width lookahead assertion that an indentation level has closed, starting at the current position. |
| {BodyWhite} |
Match the current indentation level. Initially this will be zero. It will increase when {OpenWhite} successfully matches, and decrease when {CloseWhite} successfully matches.
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