Regular Expressions are used in many programming languages and PERL is no exception here. Regular Expressions are well supported and can be useful in a lot of ways. So what are they good for? With Regular Expressions you can easily find and manipulate information in strings. Let's start with the easier one, finding information. Before I start digging in I'll list a table with some major commands you will be needing. Don't worry about their meaning – just refer to it as you need it.
\s || \S space || no space
\w || \W word || no word (word also means a combination of letters (without space))
\d || \D digit || no digit
\b || \B word border || no word border
^ beginning of line
$ end of line
[12468] quantity (iteration)
[3-7] quantity (scope)
[^456] excluded quantity (iteration)
[^3-9] excluded quantity (scope)
. any character (exept new line)
* no or any occurence
? no or one occurence
+ one or any occurence
a|b|c alternatives