The Mech plugin allows one to script interactive mechanisms in the style of block languages like Squeak. We use capitalized keywords for blocks and indent them with spaces to show where blocks nest within others.
Say "HELLO" for a friendly greeting.
HELLO
Say "HELLO world" to greet the whole world.
HELLO world
Say "CLICK" to run indented commands only when clicked.
CLICK HELLO HELLO world
CLICK expects to be followed with indented commands and will complain if it doesn't find any.
CLICK HELLO
See the Catalog of Mech Blocks for more ideas.