Man pages matching name tcl_findexecutable in section 3tcl:

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