subharanjanm/debug-bar-actions-and-filters-addon — pull request #3 by jrfnl (2013-12-22 01:20:21+00:00)
Title: Bugfix: Make sure the plugin will not give a parse error on PHP < 5.3

As closures are only available on PHP 5.3+, having one in a file used on PHP 5.2 (which is still the official WP minimum requirement), will give a parse error and bork the whole website on which the plugin is installed....

Just came across it while testing another plugin on various PHP versions.