(ps (create a 11 b 22)) => "{ a : 11, b : 22 };", which is illegal at the top level because JS interprets the curly braces as statement block delimiters. PS should probably generate "({ a : 11, b : 22 })" instead.
Similarly, (ps (lambda () 123)) =>
"function () { return 123; };"
is also illegal at the top level and should also be wrapped in parens.
Such forms obviously don't come up much in source files, but they do in a REPL. We're making a PS REPL (and source-level debugger) for Emacs, which is how we ran across them.