using bind concat in construct query

I have the following query

CONSTRUCT{
   ?entity a something;
    a label ?label .
} 
WHERE
{
   ?entity a something;
   a label ?label .
 BIND(CONCAT(STR( ?label ), " | SOME ADDITIONAL TEXT I WOULD LIKE TO APPEND MANUALLY") ) AS ?label ) .
}

I simply want to concatenate some text with ?label, however when running the query I get the following error:

BIND clause alias '?label' was previously used

I only want to return a single instance of ?label hence, I defined it in the construct clause.