试图理解遗留项目中的正则表达式[重复]

Question

This question already has an answer here:

• Reference - What does this regex mean? 1 answer

In one codebase (PHP) I'm working on currently there is this regular expression:

!([a-z0-9]*)\.([a-zA-Z0-9]{3,4})

Which supposedly should match something like this:

a1213asddaa13124312ada.12ws

And yet it does not happen. Matching occurs only with this expression:

([a-z0-9]*)\.([a-zA-Z0-9]{3,4})

Can anybody clarify?

</div>

Answer 1

! has no special meaning. It'll match a literal exclamation mark. a1213asddaa13124312ada.12ws does not start with one.