{ "blueprint":
  { "type": ["@", "rules", "CC/auto", "config_file"]
  , "input": ["foo.in"]
  , "output": ["foo.h"]
  , "magic_string": ["cmakedefine"]
  }
, "blueprint_@only":
  { "type": ["@", "rules", "CC/auto", "config_file"]
  , "input": ["foo.in"]
  , "output": ["foo.h"]
  , "magic_string": ["cmakedefine"]
  , "@only": ["true"]
  }
, "header_both":
  { "type": "configure"
  , "target": "blueprint"
  , "config":
    { "type": "let*"
    , "bindings":
      [ [ "defines"
        , [ ["FOO", "foo"]
          , ["BAR", "bar"]
          , ["NO_MAGIC_AT", "magic_at"]
          , ["NO_MAGIC_CURLY", "magic_curly"]
          ]
        ]
      ]
    , "body": {"type": "env", "vars": ["defines"]}
    }
  }
, "header_@only":
  { "type": "configure"
  , "target": "blueprint_@only"
  , "config":
    { "type": "let*"
    , "bindings":
      [ [ "defines"
        , [ ["FOO", "foo"]
          , ["BAR", "bar"]
          , ["NO_MAGIC_AT", "magic_at"]
          , ["NO_MAGIC_CURLY", "magic_curly"]
          ]
        ]
      ]
    , "body": {"type": "env", "vars": ["defines"]}
    }
  }
}