Why so many tcl's and tk's

Tue Mar 13 21:19:29 UTC 2007

Are the different versions of tcl and tk really not backwards compatible 
with earlier versions?  I can guess that there have been heated 
conversations about this, but a my look at the mailing list archives 
didn't give me anything.  But it sure would be much nicer if there was 
just a tcl and a tcl-devel port or something like that.  Are there 
really applications that need tcl83 but break on tcl84?

Stephen