This will have no effect whatsoever. The pattern match against the DSN is done case-insensitively. Here is the appropriate line from DBI.pm (version 1.50):

    # extract dbi:driver prefix from $dsn into $1
    $dsn =~ s/^dbi:(\w*?)(?:\((.*?)\))?://i
            or '' =~ /()/; # ensure $1 etc are empty if match fails
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