gluing

What does it mean when people say that Tcl is good for gluing other applications together?

Supply examples here?

• show uses of open "|process"
• show uses of exec
• show uses of stacking commands

[ cl keeps teasing us with promises to write more on this subject...]

RS also thinks of gluing as two or more powerful packages linked together with only a few lines of code - see A little XML browser where tDOM and BWidget needed only half a page for gluing into a useful app...