Man pages matching name tcl_utfbackslash in section 3tcl:

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