SPARC Solaris2.5* is what perl/Tk's was originaly delveloped on, 
so most things work. I still build regularly on Solaris2.5.1, Solaris2.6
and occasionally on Solaris7 (aka Solaris2.7).

I normally use gcc-2.8.1 and egcs-1.1.2 but have tested (occasionally) with 
SunPRO compilers.            

*** IMPORTANT Solaris7 and gcc issue *** 
There are problems with certain patches from Sun and certain gcc versions.
See gcc source distribuition or 
http://gcc.gnu.org/install/specific.html#sparc-sun-solaris2.7 
for details. 

In particular Robert <sobrika@erols.com> writes
"
By simply removing Solaris 7 patch 107058-01 from my machine I was able to
re-make Perl/Tk and pass all the post-installation tests.  Just for the record, 
I am using the gcc 2.8.1 and perl 5.00503 binary distributions from the
sunfreeware site. The perl binary was compiled with gcc 2.8.1. 
"

I have only tested with openwindows, and recommend that as an optimized X11R5
unless you really need X11R6isms (which I have not tried). 

I have one report that /usr/ccs/bin/make fails to build correctly.
I cannot reproduce the problem with current MakeMaker, but it was 
reported that using GNU make (which is what I _usually_ use) fixed the problem.

There is code to comprehend the way openwindows deals with locale issues.
The workround may _cause_ problems if you are using another X11 not openwin.