| (?-i) | set case sensitivity |
| (?i) | turn OFF case sensitivity after (?-i) |
| ^ | start of line or negates character class |
| $ | end of line |
| . | match any character (wildcard) |
| ? | 0 or 1 quantifier |
| * | 0 or more quantifier |
| + | 1 or more quantifier |
| \s | any whitespace character |
| \S | character is NOT a whitespace character |
| \w | any "word" character |
| \W | any "NON-word" character |
| \b | word boundary |
| \B | NOT a word boundary |
| \d | a decimal digit |
| \D | character is NOT a decimal digit |
| \ | general escape character (metacharacters) |
| \\ | backslash character |
| {8} | Repetition Example: match exactly 8 |
| {3,} | Repetition Example: three or more |
| {2,4} | Repetition Matches 2, 3, or 4 repetitions |
| NO (a number MUST come before the comma) | |
| ( ) | start and end of subpattern |
Metacharacters: Outside square brackets: \ ^ $ . [ | ( ) ? * + {
Metacharacters: Inside square brackets \ ^ - [ ]