rocknbil - 4:39 pm on Aug 19, 2010 (gmt 0)

I don't think you're going to be able to do that. The regexp must match the data, not the other way around, and you're asking to insert a character where there isn't one in the string, and it really can be anywhere. You could preprocess the input so it's like this, and do a long series of "or's":

where field = 'a-bcdef' or
field = 'ab-cdef' or
field = 'abc-def' ....

but that would be extremely unwieldy. You should probably re-think your front end, like

<p>Enter your product code:</p>
<p><label for="code-prefix">Prefix:</label>
<input type="text" name="code-prefix" id="code-prefix">
<label for="code-suffix">Suffix:</label>
<input type="text" name="code-suffix" id="code-suffix"></p>

Then you can do

$term = $_POST['code-prefix'] . '-' . $term = $_POST['code-sufffix'];

.... where field='$term';

This would be faster, more efficient, and less error prone anyway.