Man pages matching name tcl_deletefilehandler in section 3tcl:

Tcl_DeleteFileHandler.3tcl.en	debian 10 / tcl8.6-doc
Tcl_DeleteFileHandler.3tcl.en	debian 11 / tcl8.6-doc
Tcl_DeleteFileHandler.3tcl.en	debian 12 / tcl8.6-doc