rebol [
  title: "substring function"
  author: "vpavlu"
  date: 9-dec-2002/09:36
  home: http://plain.at/vpavlu
]

substr: func [ "returns substring starting at offset"
  str[string!]
  offset[integer!]
  /len "limit substring to given length" l
] [ 
  if not len [l: length? str]
  copy/part at str offset l
]