Symptom
Regex is a regular expression that takes as parameter a sequence of characters that defines a search pattern.
The following SAP Help document:
Has every available function in the SDK that uses regex.
Environment
SAP Cloud Applications Studio
Resolution
As every regex use-case is different from one another, there isn't one to fit all.
Note that helping with building regex fall under consulting and outside of the scope of SAP Support.
Usually, when searching on the internet for a specific use-case for regex, chances are that someone already asked your specific use-case on external sites (such as Stack Overflow).
There are also various external sites that helps with building your regex up, such as:
Which also explains each part of your regex and what it will do.
Keywords
PDI, SDK, regexp, regular expressions, text, replace, find , KBA , AP-RC-BDS-SCR , ByDesign Studio Scripting (ABSL) , How To