State machines can be a powerful way to sequence execution. This is a link to a package to implement Moore type state machines in Tcl.
http://chiselapp.com/user/mangoa01/repository/mrtools/doc/tip/moore/wiki/intro.wiki
It is rather more complete than the simpler examples on the wiki, of course, at the expense of a bit more learning curve. It is large enough that it is hard to deal with as a wiki page, so I have put it in Fossil repository that I have been building for some of these types of tools.