anchor.diff:     ())
   
     (pipeline
  -   (pipe-sequence)
  -   (bang pipe-sequence))
  +   (bang pipe-sequence)
  +   (pipe-sequence))
   
     (pipe-sequence
      (command pipe-sequence-tail))
  
positive.code:    ())
  
    (if-clause
     (if-word compound-list then compound-list else-part fi)
     (if-word compound-list then compound-list fi))
  
    (else-part
     (elif compound-list then else-part)
     (else compound-list))
  
    (while-clause
  
negative.code:    (lparen compound-list rparen))
  
    (compound-list
     (term separator)
     (term)
     (newline-list term separator)
     (newline-list term))
  
    (term
     (and-or term-tail))
  