| 
          
            
              | [abc] | A single character of: a, b or c |  
              | [^abc] | Any single character except: a, b, or c |  
              | [a-z] | Any single character in the range a-z |  
              | [a-zA-Z] | Any single character in the range a-z or A-Z |  
              | ^ | Start of line |  
              | $ | End of line |  
              | \A | Start of string |  
              | \z | End of string |  | 
          
            
              | . | Any single character |  
              | \s | Any whitespace character |  
              | \S | Any non-whitespace character |  
              | \d | Any digit |  
              | \D | Any non-digit |  
              | \w | Any word character (letter, number, underscore) |  
              | \W | Any non-word character |  
              | \b | Any word boundary |  | 
        
          
            | (...) | Capture everything enclosed |  
            | (a|b) | a or b |  
            | a? | Zero or one of a |  
            | a* | Zero or more of a |  
            | a+ | One or more of a |  
            | a{3} | Exactly 3 of a |  
            | a{3,} | 3 or more of a |  
            | a{3,6} | Between 3 and 6 of a |  |