Please could somebody enlighten me on the ins and outs of the following error message.

Use of uninitialized value in join or string at C:/Perl_activate/20_Oc
+tober_2005_L.pl line 438, <FLAT_FILE> line 1191.
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in relation to the following code.

    my $sth_C = $dbh->prepare($Return_results) or die "Couldn't prepar
+e query: ".$dbh->errstr;
    
    $sth_C->execute() or die "Couldn't execute query: ".$sth_C->errstr
+;
    
        while (my @row = $sth_C->fetchrow_array) {
             
      print OUTPUT_FILE join("\t", @row);  ###<< The error message app
+lies to this line of code.
      print OUTPUT_FILE "\n";
      
      undef @row;
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