This function checks if the specified variable exists, in other words: contains a value. A variable that once was set and later on unset does also not exist.
The function accepts a single argument, which needs to be a variable. It returns 0 if the variable does not exist and 1 otherwise. The function can be combined with any other expression to form more complec expressions.
New in version 8.2010.10.
if exists(!$path!varname) then ... if not exists($.local!var) then ... if exists($!triggervar) and $msg contains "something" then ...
Help with configuring/using