Set the DBI attribute 'FetchHashKeyName' to 'NAME_lc' for getting the field name in lower case. For eg:

#For getting the lower case
$dbh->{FetchHashKeyName} = 'NAME_lc';
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#For getting the upper case
$dbh->{FetchHashKeyName} = 'NAME_uc';
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For more information, please go through FetchHashKeyName