Character Meaning
\ Escape, do not interpret the following meta-character
| OR, match either of the alternatives
( ) Create a single expression or atom
{ } Define the minimum and/or maximum repetitions of an atom
* Match an atom zero or more times
+ Match an atom one or more times
? Match an atom zero or one times
^ Match an atom at the start of the string
$ Match an atom at the end of the string
[ ] Match one of the enclosed atoms
. Match any character
\A Alternative to meta-character ^
\Z Alternative to meta-character $
|