GPDL $GREP
$GREP is a regular-expression compiler and search engine. If you know what that means then all is well. Otherwise you should check out the topic "regular expressions".
$GREP implements 'egrep' regular expressions.
$GREP ( regularExpression, string)
Return value:
The string is searched using the regular expression and returns true ("1") or false ("") depending on whether a match is or is not successful.
As a side-effect, if the match is successful, any substrings that were matched are put safely away where you can reference them before using $GREP (or $GCASE) again. You reference these sub-strings with $WIGGLE.