You may be writing within
<package>/tcl/ad-proc-library.tcl
They are cached by Naviserver. To apply your amends, and get results instantly, you must put your library, or any other, in the watch list, by clicking in the link "Changed", in the developer's navigation header. Visit: /acs-admin/apm/?reload_links_p=1
A drastic option would be to restart NaviServer. Depending on the hardware, booting up a clean installation would be fast.
So, to write Tcl code and see the results instantly you can use the "Developer watch list", or write you can place your code within /www or /packages/your-pkg/www/
p.s. forget about ASP. not everything! :)