I believe the main test here needs to be for "", not for definedness. DBI is going to give him an array, and some of the values in it may be empty strings, if I understand the problem correctly. The empty strings are what needs to be replaced. I think this variation will do the job: 
my @results_tmp = map {($_ ne "") ? "$_" : "--"} @results;
print join(",", @results_tmp),"\n";

[download]
For those who aren't comfortable with map, this is about the same as: 
my @results_tmp = @results;
($_ eq "") && ($_ = "--") for @results_tmp;
print join(",", @results_tmp),"\n";

[download]

In reply to Re: Re: Substituting '--' for Nulls by virtualsue
in thread Substituting '--' for Nulls by johnirl

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.