I ran locate on tcl.h and got these results:
[HondaATC@server134 eggdrop1.6.18]$ locate tcl.h
/home/HondaATC/tcl/include/tcl.h
/home/HondaATC/tcl8.4.17/generic/tcl.h
/home/HondaATC/tcl8.4.17/tools/tcl.hpj.in
/home/HondaATC/tcl8.4.17/win/tcl.hpj.in
[HondaATC@server134 eggdrop1.6.18]$
So I modified the command you posted earlier to reflect the usr/tcl/include/ path and it still didn't work
configure: warning:
The file '/usr/tcl/include/tcl.h' given to option --with-tclinc is not valid.
configure will now attempt to autodetect both the Tcl library and header.
checking for Tcl library... using /lib
checking for Tcl header... using /
checking whether the Tcl system has changed... yes
checking for Tcl version...
checking for Tcl patch level...
configure: error:
Your Tcl version is much too old for Eggdrop to use. You should
download and compile a more recent version. The most reliable
current version is 8.4.6 and can be downloaded from
ftp://tcl.activestate.com/pub/tcl/tcl8_4/.