Looks like it's something to do with your platform, because your case three works fine on OS X (10.3.5):

$ sudo perl -de 0
[ ... ]
  DB<1> x $>, $)
0  0
1  '0 262 80 31 20 5 4 3 2 1 0'
  DB<2> ( $>, $) ) = ( 501, "20 20 80" )

  DB<3> x $>, $)                        
0  501
1  '20 80 20'
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