If we're being nitpicky :) no need to create a lexical block for map:

$ perl -Mstrict -MData::Dumper -we'my%h=( (map +($_=>2), "B","C","D"),
+ one=>1 ); print Dumper(\%h)'
$VAR1 = {
          'one' => 1,
          'D' => 2,
          'C' => 2,
          'B' => 2
        };
[download]