Others have pointed out that the problem should be in your $dbh not being defined.
However, there is something else that will give you problems, once you fix the $dbh business.
fetchrow_array returns an array, not a scalar, so your result variable should be @results.

update
Unless you want to get the first column only, as johannz reminds. Thanks.
However, be aware that, according to DBI docs, the result of fetchrow_array in scalar context is undefined. Therefore, it's better to ask for the result always in list context.

If you want to use a scalar, then the method to call is fetchrow_arrayref, which returns an array reference.

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