== String#splice

  require 'facets/string/splice'

  a = "HELLO"
  a.splice(1).assert == "E"
  a.assert == "HLLO"

range

  a = "HELLO"
  a.splice(1..2).assert == "EL"
  a.assert == "HLO"

store

  a = "HELLO"
  a.splice(1, "X")
  a.assert == "HXLLO"

This could be done if class of 2nd arg is checked.

  #Unit :splice_length
  #  a = "HELLO"
  #  a.splice(1,2).assert == "EL"
  #  a.assert == "HLO"
  #end

