tie my(%lc_hash), 'Hash::Case::Lower';
{
    my $href = retrieve( ... );
    while ( my ( $k, $v ) = each %$href )
    {
        $lc_hash{$k} = $v;
    }
}

##</code><code>##

# writing it out
store( \%lc_hash, ... );

# reading it in
my $lc_href = retrieve( ... );
bless $lc_href, 'Hash::Case::Lower';