Associated with the Cut, Copy and Paste functions, the selection functions do work between Windows apps and Tcl/Tk scripts. 

To see this, try the following: select some text in Microsoft Word, Write or any other Windows app. Copy the data to the clipboard
(inside the app). Then, enter the following at your wish prompt: 

set clip [selection get -selection CLIPBOARD ]

The variable clip should now hold the data from the clipboard. 

The parts that may be troublesome are that: 

       UNIX apps tend to use an active copy and paste with the PRIMARY selection. 

       Windows apps tend to use a passive copy and paste, placing the data in the clipboard as an intermediary stopping point
       between the applications. 

       Motif applications on Unix do use the CLIPBOARD selection. Decoding the Motif clipboard is a left as an exercise for the
       reader. 

       The X selection mechanism handles a lot more than text, which introduces some interesting complexity. 

All in all, Tk does pretty good with handling selections on multiple operating systems. 

-Eric Foster-Johnson