Man pages matching name itcl in section 3itcl:

itcl.3itcl.en	debian 10 / itcl3-doc
itcl.3itcl.en	debian 10 / tcl-itcl4-doc
itcl.3itcl.en	debian 11 / itcl3-doc
itcl.3itcl.en	debian 11 / tcl-itcl4-doc
itcl.3itcl.en	debian 12 / itcl3-doc
itcl.3itcl.en	debian 12 / tcl-itcl4-doc