You may know what regular expressions are for, but are unfamiliar with their syntax.
What is a regular expression
With regular expressions you can describe general text patterns. Find that email in the haystack!
Literals will literally (yeah, it's accurate to use it here) match the character you describe. If you're look for
trouble, you'll find
The meat of the matter. They will match not one character, but a group of them. This is when lazyness pays off.
Change your regular expressions behavior just by sending one of these. Go through multiple lines, ignore the casing, or find all the matched patterns.
You are able to read and write some regular expressions.
Give some steroids to your characters (or groups) by quantifying them.
? will make them optional,
+ will allow for 1 or more, and
* to 0 or more.
Wrap your characters in a group, so they're now another building block that you can quantify, or to do some back-referencing.
I don't get enough by finding pieces of text. I want to reuse them. Morph them into something different.
You know how to read and understand most of the expressions you find.
Sometimes, describing what you want to match is not enough. Sometimes you also need to describe the context.
You can achieve the task you want in many different ways, so it becomes necessary to discard some of them by how complex and inefficient they are.
When writing sufficiently loose expressions turns them Evil, risking you to Regular Expression Denial of Service. Doesn't sound good. And it isn't.