Fix the request/response header error

    than once.</dd>

    <dt><code>merge</code></dt>

    <dd>The response header is appended to any existing header of

    <dd>The request header is appended to any existing header of

    the same name, unless the value to be appended already appears in the

    existing header's comma-delimited list of values.  When a new value is

    merged onto an existing header it is separated from the existing header

    <var>value</var> must be omitted.</dd>

    <dt><code>edit</code></dt>

    <dd>If this request header exists, its value is transformed according

    <dd>If this response header exists, its value is transformed according

    to a <glossary ref="regex">regular expression</glossary>

    search-and-replace.  The <var>value</var> argument is a <glossary

    ref="regex">regular expression</glossary>, and the <var>replacement</var>