Use compgen -W instead of grepping $cur.

contrib/mplayer

@@ -7,10 +7,9 @@ have mplayer && {
 _mplayer_options_list()
 {
 	cur=${cur%\\}
-	COMPREPLY=( $( $1 $2 help 2> /dev/null | \
+	COMPREPLY=( $( compgen -W "$( $1 $2 help 2>/dev/null | \
 		sed -e '1,/^Available/d' | awk '{print $1}' | \
-		sed -e 's/:$//' -e 's/^'${2#-}'$//' -e 's/<.*//' | \
-		grep "^$cur" ) )
+		sed -e 's/:$//' -e 's/^'${2#-}'$//' -e 's/<.*//' )" -- $cur ) )
 }
 
 _mplayer()