Nested debugging

Sometimes you are inside the debugger and want to debug start debugging another method or Ruby expression of your choosing. You can do this with the debug debugger command:

  (trepan): gdb(3,5)  # This evaluates without debugging into
  D=> 1
  (trepan): debug gcd(3,5)  # This debugs into gcd
  ENTERING NESTED DEBUGGER
  METHOD Object#gcd(a, b)
  -> (gcd.rb:4)
  def gcd(a, b)
  ((trepan)):  step  
  -- (gcd.rb:6)
  if a > b
  ((trepan)): continue
  LEAVING NESTED DEBUGGER
  R=> 1
  (gcd.rb:18) a, b = ARGV[0..1].map {|arg| arg.to_i}
  (trepan): 

Every time you nest debugging a new level of parenthesis is added. So ((trepan)) indicates you are nested once in the debugger.