See Hash::Rename
Renaming hash's keys in place

#!/usr/bin/perl -w 
use strict;
use Hash::Rename;

my %h = ( 
    '.111' => 'Aaaa',
    '.222' => 'Bbbb',
    '.333' => 'Cccc'
);

hash_rename %h, code => sub { s/.{2}// };

__END__

Output:

$VAR1 = {
          '22' => 'Bbbb',
          '11' => 'Aaaa',
          '33' => 'Cccc'
        };
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hth,
PooLpi