🚀 go-pugleaf

I was studying example #19 in the blue book today and I came across a
line that I don't understand.  The program runs so it must make sense to
the interpreter, but it doesn't make sense to me.

When creating a new font dictionary, this example uses this line:

{ exch newfont 3 1 roll put }

"newfont" appears to be a new empty dictionary. I don't understand how
newfont is being accessed and used here.  If one enters a string without
the "/", the interpreter trys to find it in the dictionaries.  Shouldn't this
return some kind of "can't find" error?  It seems to do this if you set
this up and try to run it by itself.

I really need to understand this so I can create some new fonts for
myself.  Would someone please explain in more detail what is going on
here?  Thanks for the reality.