use Data::Dumper;
$hash{keya} ;
$hash{keyb} ;
$hash{keyc} ;

$hash{keya}{1} = "fooA";
$hash{keya}{2} = "barA";
$hash{keyb}{1} = "fooB";
$hash{keyb}{2} = "barB";
$hash{keyc}{1} = "fooC";
$hash{keyc}{2} = "barC";

print Dumper (\%hash);

__output__

$VAR1 = {
          'keya' => {
                      '1' => 'fooA',
                      '2' => 'barA'
                    },
          'keyb' => {
                      '1' => 'fooB',
                      '2' => 'barB'
                    },
          'keyc' => {
                      '1' => 'fooC',
                      '2' => 'barC'
                    }
        };


##</code><code>##

use Data::Dumper;
$hash{keya} = "";
$hash{keyb} = "";
$hash{keyc} = "";

$hash{keya}{1} = "fooA";
$hash{keya}{2} = "barA";
$hash{keyb}{1} = "fooB";
$hash{keyb}{2} = "barB";
$hash{keyc}{1} = "fooC";
$hash{keyc}{2} = "barC";

print Dumper (\%hash);

__output__

$VAR1 = {
          'keya' => '',
          'keyb' => '',
          'keyc' => ''
        };