gaim depends on tcl

[Pete Zaitcev]

Hi, Christopher & others:

the gaim-0.75-1.3.0 requires tk & tcl, which I do not have installed,
so I went to investigate. The spec does not mention tcl anywhere.
So, obviously, during the build process, configuration picks
an installed libtcl/libtk, then somehow informs rpm that these
libraries are required. How does it actually happen?

I saw specs which have small sections like so

%{expand:%%define buildforrh7 %(A=$(awk '{print $5}' /etc/redhat-release); if [ "$A" = 7.2 -o "$A" = 7.3 ]; then echo 1; else echo 0; fi)}
......
%if %buildforrh7
BuildRequires:  nautilus2-devel
%endif

I could understand if gaim spec had a scriptlet which parsed the output
of ./configure and set something like %wehavetcl, then added a Requires
like the above. But this is not what is happening. Can you enlighten me
about the magic workings in the case of gaim?

Thank you,
-- Pete

P.S. Aside from the spec magic, why would a modern application require tcl?