A regular expression, “regexp”, is a formidable phrase denoting something which is conceptually very simple. A regular expression is an expression that denotes a pattern, coded in a small language designed for just that. The basic special symbols are as follows:
. any one character
* zero or more of the preceding character
^ beginning of line
$ end of line
[a-z] a set of characters [a-z] is the whole lower-case alphabet
