(Sorry about the apparently redundant question; I started typing it before your answer showed up on the bboard.)
The only sparc I have is a SS 10 and it works fine there... It's possibly related to your 64-bit architecture. (There have been bugs with tcl on 64 bit machines before, but nothing recent that I could find.) Do you have the most recent version of tcl installed, and did you try this in tclsh?