This applies to Servlet API (need for Cross-Container solution working at Tomcat, WebSphere 6.0.2,6.1,7.x , and others), as well as to ASP.NET Runtime (2+) on IIS 5.1 (and maybe others not tested) with standard modules in action.
GET /UriHandler.aspx/[%5d HTTP/1.1
Mission: tell me THE MAGIC API to achieve this.
Also wanted: description and comparative tables describing IIS and ASP.NET URL normalization with IIS 5,6,7, with/without URLScan and other URL related HTTP.sys and other settings. I mean complete IIS URL handling stack for all IIS versions ;-)