Perl Tips Blog from Bay View Training

One of regular expressions’ most useful features is memorization. To do this, just put parentheses around part of your expression and the result will be memorized:

my($name) = /hello, (\w+)/

In this example, we look in $_ for the word “hello” followed by a comma, space, and a word. Since the word, \w+, has parentheses around it, the part of the string that it matches gets memorized. In this example, we are assigning the return value of the regular expression match to $name. So if $_ contains “hello, world” then $name gets “world” - very convenient.

But parentheses also do other things besides memorize their contents, and this feature can become annoying. Here’s an example. (more…)