Pattern What the pattern matches
^ Beginning of string
$ End of string
. Any single character
[...] Any character listed between the square brackets
[^...] Any character not listed between the square brackets
p1|p2|p3 Alternation; matches any of the patterns p1, p2, or p3
* Zero or more instances of preceding element
+ One or more instances of preceding element
{n} n instances of preceding element
{m,n} m through n instances of preceding element