Not sure what you consider cool. Here's my balance between terse and obvious:

  /(....)(..)(..)/;
  $dt = DateTime->new( year => $1, month => $2, day => $3 );
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I suppose one could try to get a little clever by doing something like

  my %th; @th{qw( year month day )} = /(....)(..)(..)/;
  $dt = DateTime->new( %th );
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I don't know if that's any "cooler", though.