The difference is that you are actually printing the thing you are incrementing rather than incrementing one item and printing another completely distinct item. What the OP did is more like the final print statement here: 
perl -E '
  my ( $x, $y, $z ) = ( 1, 2, 3 );
  my @a = ( $x, $y, $z );
  say join " ", map { $_++, $_ } @a;
  say "@a";
  say "$x $y $z";
'
1 2 2 3 3 4
2 3 4
1 2 3

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In reply to Re^5: Array of variables by frozenwithjoy
in thread Array of variables by rtteal

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