regular expressions

egular Expression Operators

a?	matches 0 or 1 occurrence of *a*	'a' or empty string
a*	matches 0 or more occurrences of *a*	empty string or 'a', 'aa', 'aaa', etc
a+	matches 1 or more occurrences of *a*	'a', 'aa', 'aaa', etc
a|b	match *a* or *b*	'a' or 'b'
.	match any single character	'a', 'q', 'l', '_', '+', etc
[woeirjsd]	match any of the named characters	'w', 'o', 'e', 'i', 'r', 'j', 's', 'd'
[1-9]	match any of the characters in the range	'1', '2', '3', '4', '5', '6', '7', '8', '9'
[^13579]	match any characters not named	even digits, or any other character
(ie)	group an expression (for use with other operators)	'ie'
^a	match an *a* at the beginning of a line	'a'
a$	match an *a* at the end of a line	'a'

There are a couple of other things you should know. If you want to use one of the operators above to mean the actual character, like you want to match a question mark, you need to put a '\' in front of it. For example:

// evaluates to true, and will for anything ending in a question mark (that doesn't have a question mark in it) "How tall is Angelina Jolie?" ==~ /[^\?]+\?/

This is your first really ugly regular expression. (The frequent use of these in PERL is one of the reasons it is considered a "write only" language). By the way, google knows how tall she is. The only way to understand expressions like this is to pick it apart:

/	[^?]	+	?	/
begin expression	any character other than '?'	more than one of those	a question mark	end expression