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## Pitfalls

The following list contains interesting hints, that are not really restrictions, but have to be handled carefully.

- Using {} and ''''.
  Tcl commands bound to events or resources can be surrounded with {} or ''''. The use of {} is much safer, than the use of ''''. The code surrounded by '''' is parsed and substitutions are performed, when the binding is added or the resource is set. This may lead to unwanted results. It is better to use global variables to pass parameters into commands bound to events or resources.
- Setting auto_path.
  If the loaded source sets the auto_path variable, it should check if it is started inside of XF . Manipulating the auto_path variable can make XF inoperable.