A regular expression is a string that specifies a complex search phrase. In most cases the string is preceded by an exclamation point (!). By using special characters such as a period (.), asterisk (*), caret (^), and brackets ([ ]), you define the conditions of the search. Regular expressions can be used in the following cases: Within the physical description of a window or object in the GUI Map. Within a GUI checkpoint, when verifying the contents of an edit field or static text object. Within TSL functions that search for text, such as win_find_text and obj_find_text.