gistfile1.txt

@prefix : <urn:example:> .
@prefix log: <http://www.w3.org/2000/10/swap/log#> .
@prefix string: <http://www.w3.org/2000/10/swap/string#> .

:Let :string "hello world" .

(_:X _:Y) log:negativeSurface {
    :Let :string _:X .

#    _:X string:upperCase _:Y .

    () log:negativeSurface {
       :Let :capitalize true .
       :Let :capitalize _:Y .
    }
} .

# Filter out what to see in the output
(_:P _:O) log:querySurface {
    :Let _:P  _:O . 
} .

(_:L _:R) log:querySurface {
    _:L :capitalize _:R .
} .