This error message is saying that:

my $nRows_affected = $feed_table_ext_results->execute(..)
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was never executed. Why that is, I don't know at the moment, but it appears that there a number of posts that address this issue.

Please adjust the formatting of your code to something similar to this:

while (my @insert_ext = $feed_table_ext_results->fetchrow_array())
{
   $ext_insert->execute(@insert_ext) ;
}
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Instead of what you posted:

while (my @insert_ext = $feed_table_ext_results>fetchrow_array())
                                        {
         
                  $ext_insert->execute(@insert_ext) ;
                                        }
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The Perl compiler doesn't care about huge indentations of the braces, but the humans do care.