Regular expression pattern used to match dynamic strings in a specific format. The dynamic strings are enclosed in double square brackets ([[~ {key} ... ~]]). The format inside the double square brackets follows a specific pattern. This regular expression is used to extract and process the dynamic strings.

Whatever is passed in between the first set of curly braces is the key used to access the data from the data/ctx object. passed in. Anything after that is parsed as a series of cases, which are used to determine the value of the dynamic string.