DB<49> undef @x

  DB<50> x [ shift @x, splice @x,0,1 ]
0  ARRAY(0x34a5270)
   0  undef
  DB<51> @x=()

  DB<52> x [ shift @x, splice @x,0,1 ]
0  ARRAY(0x34a6c48)
   0  undef
  DB<53>