The Ruby Way: Solutions and Techniques in Ruby Programming, Second Edition

3.1. Regular Expression Syntax

The typical regular expression is delimited by a pair of slashes; the %r form can also be used. Table 3.1, “Basic Regular Expressions,” gives some simple examples:

Table 3.1. Basic Regular Expressions

Regex	Explanation
/Ruby/	Match the single word Ruby
/[Rr]uby/	Match Ruby or ruby
/^abc/	Match an abc at beginning of line
%r(xyz$)	Match an xyz at end of line
%r|[0-9]*|	Match any sequence of (zero or more) digits

It is also possible to place a modifier, consisting of a single letter, immediately after a regex. Table 3.2 shows the most common modifiers:

Table 3.2. Regular Expression Modifiers

Modifier	Meaning
i	Ignore case in regex
o	Perform expression substitution only once
m	Multiline mode (dot matches newline)
x	Extended regex (allow ...