What do the bars on top mean (if they are bars/pipes) ?
If you mean |s f| then that is simply stating s and f are variables.
You would highlight/select a block of text (e.g. |s ... ^f), click, select "execute", which causes the selected text to be compiled, executed, and the result (f in this case) shown in an object browser.
If that sounds like what happens in IDEs, you would be right: they
all took their inspiration from Smalltalk. As did the entire Sun and Macintosh GUIs, of course.
Smalltalk also invented the "refactoring browser" - but that was relatively recently in the early 90s.