$output = $output . "<td$recentChange><div title=\"Changed by $moduleF
+ie
ld[1] at $localtime\" class=table_data onClick=\"ToggleShowHide('label
+_$headers[$dataCount]$moduleCount','$headers[$dataCount]$moduleCount'
+)\" id=\"label_$headers[$dataCount]$moduleCount\" style='display: blo
+ck;'>$moduleField[0]</div> <div id=\"$headers[$dataCount]$moduleCount
+\" style='display: none;'><input type=text name=\"$headers[$dataCount
+]$moduleCount\" value=\"$moduleField[0]\"><input type=button onClick=
+\"ToggleShowHide('label_$headers[$dataCount]$moduleCount','$headers[$
+dataCount]$
moduleCount')\" value=OK></div></td>";
[download]

.... is pretty darned ugly (no offense intended).

You could tidy that up somewhat, and make it a bit more readable, by doing something like:

$output .= qq(
    <td$recentChange>
        <div title="Changed by $moduleField[1] at $localtime"
            class=table_data
            onClick="ToggleShowHide('label_$headers[$d_cnt]$m_cnt','$h
+eaders[$d_cnt]$m_cnt')"
            id="label_$headers[$d_cnt]$m_cnt"
            style='display: block;'>
            $moduleField[0]
        </div>
        <div id="$headers[$d_cnt]$m_cnt"
            style='display: none;'>
            <input type=text name="$headers[$d_cnt]$m_cnt" value="$mod
+uleField[0]">
            <input type=button
                onClick="ToggleShowHide('label_$headers[$d_cnt]$m_cnt'
+,'$headers[$d_cnt]$m_cnt')"
                value=OK>
        </div>
    </td>
    );
[download]

Notes:

• $foo .= $bar is the same as $foo = $foo . $bar
• use the quoting operators (qq - look for "Regexp Quote-Like Operators" in perlop) in preference to double-quotes - saves lots of messing about escaping special characters.
• Whilst descriptive variable names are generally considered a good thing™, if you make them too long you wind up with big long statements like the one above, that are difficult to read and understand. Consider shortening some of your variable names - especially those that have limited scope. A good rule of thumb is that the shorter the scope, the shorter the name.
• When you have a big long statement like the one above, split it over several lines and use indenting for vertical alignment, to improve readability (and make debugging easier).

Hope this helps,
Darren :)