Problem

• Originally posted to Perl quiz-of-the-week.
• Input:

  ALDA.D
  ALDA.Q
  ALDA.W
  AMTA.B
  AMTA.E
  AMTA.M
  AMTA.X
  BMX.F
  C.X
  DMZ.A
  DMZ.X
  

• Output:

  ALDA.D
  ALDA.M
  ALDA.Q
  ALDA.W
  AMTA.B
  AMTA.E
  AMTA.M
  AMTA.X
  BMX.F
  BMX.M
  C.M
  C.X
  DMZ.A
  DMZ.M
  DMZ.X