When enabled, this pragma warns about indirect method calls that are present in your code. This pragma currently does not warn for core functions (print, say, exec or system). This may change in the future, or may be added as optional features that would be enabled by passing options to unimport. In http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-fatal, Matt S. Trout gives an example of an undesirable indirect method call on a block that can cause a particularly bewildering error.