Racket, Gauche, MIT, Gambit, Chicken, Bigloo, Kawa, SISC, Chibi, Chez, Ikarus/Vicare, STklos, KSi, Rep, Oaklisp, Owl Lisp all understand |...| syntax.
Scsh, Guile, SCM, NexJ, Shoe, TinyScheme, Dream, Scheme 7, BDC, Elk, UMB, VX treat | as an ordinary identifier character.
Scheme48, Larceny, Ypsilon, Mosh, SigScheme, RScheme, XLisp, Schemik all report syntax errors.
IronScheme gets hung up reading characters from the input.