⚠️ NOTE: If you have any questions regarding the content presented below, feel free to post them here. I will be happy to help anyway I can! Regex is a big passion of mine and I look forward to hearing from you. 😁

POSIX is a special kind of character class bracket expression. It uses lower case references and functions similar to the metacharacters we I demonstrated earlier.
Here are a few examples:
[[:alnum:]]
=~ Alphanumeric characters
[[:alpha:]]
=~ Alphabetic characters
[[:digit:]]
=~ Digits
[[:ascii:]]
=~ ASCII characters
[[:punct:]]
=~ Punctuation and symbols
[[:lower:]]
=~ Lowercase letters
[[:space:]]
=~ All whitespace including line breaks
[[:cntrl:]]
=~ Control characters
Example: [[:punct:]]

NOTE: The Portable Operating System Interface is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems.
mOAR