learn regular expressions

Check out CPAN for the Perl module called Regex::Common. It has pre-built regexes for many common things so that you don’t have to bang your head against the wall.

http://search.cpan.org/dist/Regexp-Common/

e.g: # we require that $replacement be JUST a valid IP address
die “Invalid IP address provided: [$replacement]”
unless $replacement =~ m/^$RE{net}{IPv4}$/;

http://www.wilsonmar.com/1regex.htm

There are a lot of good examples, like matching IP addresses and MAC addresses.

I found a website listing a large number of common regex patterns:

regexlib

First, I read this guide.

Next, here’s an example to puzzle over:

sentence.gsub( /\([-\w]+\)/, ’’ )

This example will find the literal parens characters with one or more words in between and replace them with nothing.