|   |   | 
| $addon.exists Checks if an addon is currently installed | 
| Usage | 
| <boolean> $addon.exists(<id:string>[,<version:string>]) | 
| Description | 
| Returns 1 if the addon with the specified <id> is currently installed and 0 otherwise. If <version> is specified then any addon with a version lower than <version> is ignored (so you can effectively check if a greater or equal version is present). |