[Sweet]

function myConcat(){
  if( typeof arguments[ 0 ] == "string" && arguments.length == 1 )
    return ( arguments[ 0 ].match( /\w+/g ) || [] ).join( "," );
  return Array.prototype.slice.call( arguments ).join( "," );
};

alert(
  myConcat( "red", "orange", "blue" ) == myConcat( '"red", "orange", "blue"' )
);