Translations:User:Psychoslave//Lua reference manual translation stub/1761/en


 * a single character class, which matches any single character in the class;
 * a single character class followed by ' ', which matches 0 or more repetitions of characters in the class. These repetition items will always match the longest possible sequence;
 * a single character class followed by ' ', which matches 1 or more repetitions of characters in the class. These repetition items will always match the longest possible sequence;
 * a single character class followed by ' ', which also matches 0 or more repetitions of characters in the class. Unlike ' ', these repetition items will always match the shortest possible sequence;
 * a single character class followed by ' ', which matches 0 or 1 occurrence of a character in the class;
 * , for n between 1 and 9; such item matches a substring equal to the n-th captured string (see below);
 * , where x and y are two distinct characters; such item matches strings that start with x, end with y, and where the x and y are balanced. This means that, if one reads the string from left to right, counting +1 for an x and -1 for a y, the ending y is the first y where the count reaches 0. For instance, the item  matches expressions with balanced parentheses.


 * , a frontier pattern; such item matches an empty string at any position such that the next character belongs to set and the previous character does not belong to set. The set set is interpreted as previously described. The beginning and the end of the subject are handled as if they were the character '\0'. Note that frontier patterns were present but undocumented in Lua 5.1, and officially added to Lua in 5.2. The implementation in Lua 5.2.1 is unchanged from that in 5.1.0.