>perl -wMstrict -MData::Dumper -le
"my $hr = { qw(a 1  b 2  c 3  d 4) };
 print Dumper $hr;
 $hr->{ uc() } = $hr->{$_} for keys %$hr;
 print Dumper $hr;
 $hr->{ uc() } = delete $hr->{$_} for keys %$hr;
 print Dumper $hr;
"
$VAR1 = {
          'c' => '3',
          'a' => '1',
          'b' => '2',
          'd' => '4'
        };

$VAR1 = {
          'A' => '1',
          'a' => '1',
          'd' => '4',
          'B' => '2',
          'c' => '3',
          'b' => '2',
          'C' => '3',
          'D' => '4'
        };

$VAR1 = {
          'A' => '1',
          'B' => '2',
          'D' => '4',
          'C' => '3'
        };