Calculates the set of unambiguous abbreviations for the strings in self. If passed a pattern or a string, only the strings matching the pattern or starting with the string are considered.

  %w{ car cone }.abbrev   #=> { "ca" => "car", "car" => "car",
                                "co" => "cone", "con" => cone",
                                "cone" => "cone" }

[Source]

# File abbrev.rb, line 90
  def abbrev(pattern = nil)
    Abbrev::abbrev(self, pattern)
  end