>>>>> "Y" == Yukihiro Matsumoto <matz / netlab.co.jp> writes:

Y>    a b c, d

    a(b([c, d]))

Guy Decoux

p.s.:

pigeon% ~/ruby/ruby-1.4.2/ruby -Dtx -e 'a b c, d'
LOAD_FILE HRF /tmp/rbL9Oo6Y
==============================> 

NEWLINE </tmp/rbL9Oo6Y:1>
FCALL a 
  ARRAY
    FCALL b 
      ARRAY
        VCALL c 
        VCALL d 

==============================> 

rb_eval </tmp/rbL9Oo6Y:1> : NEWLINE
rb_eval </tmp/rbL9Oo6Y:1> : FCALL a
rb_eval </tmp/rbL9Oo6Y:1> : FCALL b
rb_eval </tmp/rbL9Oo6Y:1> : VCALL c
/tmp/rbL9Oo6Y:1: undefined local variable or method `c' for #<Object:0x40173ed4> (NameError)
pigeon% 

 :-)