Guide on how to create the Pattern for regular expression

Will be good to have the workflow system guide us on how to form the regular expressions and to show some examples to guide the formulation of the syntax to be inserted to the Pattern box (https://help.nintex.com/en-us/nintex2010/help/workflow/RootCategory/Actions/Nintex.Workflow.RegularExpression.htm#:~:text=A%20regular%20expression%20is%20a,regular%20expression%20with%20different%20text.)