Checks if a string starts with a search regular expression
StartsWithRegexp("123456", "[1-3]") → true
StartsWithRegexp("Australia", "[a-c]") → falseStartWithRegexp(string, searchRegexp, [isCaseSensitive])
string - A text value to search in
searchRegexp - Regular expression to search for
[isCaseSensitive] - [optional: true by default**]** - Set false if search should be case insensitive