error on script rebuild index

Hello,
With this following script, There is an error on execution :

Msg 102, Level 15, State 1, Line 21
Incorrect syntax near '('.
Executed: ALTER INDEX [IX_STADE_PERIODE_UNIQUE] ON [dbo].[STADE_AFFAIRE_PERIODE] REORGANIZE

DECLARE @command nvarchar(Max)

SELECT @command = 'USE [?]
SET NOCOUNT ON;
SET QUOTED_IDENTIFIER ON;
DECLARE @objectid int;
DECLARE @indexid int;
DECLARE @partitioncount bigint;
DECLARE @schemaname nvarchar(130);
DECLARE @objectname nvarchar(130);
DECLARE @indexname nvarchar(130);
DECLARE @partitionnum bigint;
DECLARE @partitions bigint;
DECLARE @frag float;
DECLARE @command nvarchar(4000);

SELECT
    object_id AS objectid,
    index_id AS indexid,
    partition_number AS partitionnum,
    avg_fragmentation_in_percent AS frag
INTO #work_to_do
FROM sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL , NULL, ''LIMITED'')
WHERE avg_fragmentation_in_percent > 10.0 AND index_id > 0;

DECLARE partitions CURSOR FOR SELECT * FROM #work_to_do;

OPEN partitions;

WHILE (1=1)
    BEGIN;
        FETCH NEXT
           FROM partitions
           INTO @objectid, @indexid, @partitionnum, @frag;
        IF @@FETCH_STATUS < 0 BREAK;
        SELECT @objectname = QUOTENAME(o.name), @schemaname = QUOTENAME(s.name)
        FROM sys.objects AS o
        JOIN sys.schemas as s ON s.schema_id = o.schema_id
        WHERE o.object_id = @objectid;
        SELECT @indexname = QUOTENAME(name)
        FROM sys.indexes
        WHERE  object_id = @objectid AND index_id = @indexid;
        SELECT @partitioncount = count (*)
        FROM sys.partitions
        WHERE object_id = @objectid AND index_id = @indexid;

        IF @frag < 30.0
            SET @command = N''ALTER INDEX '' + @indexname + N'' ON '' + @schemaname + N''.'' + @objectname + N'' REORGANIZE'';
        IF @frag >= 30.0
            SET @command = N''ALTER INDEX '' + @indexname + N'' ON '' + @schemaname + N''.'' + @objectname + N'' REBUILD'';
        IF @partitioncount > 1
            SET @command = @command + N'' PARTITION='' + CAST(@partitionnum AS nvarchar(10));
        EXEC (@command);
        PRINT N''Executed: '' + @command;
    END;

CLOSE partitions;
DEALLOCATE partitions;

DROP TABLE #work_to_do;

'

print @command
EXEC sp_MSforeachdb @command

Thanks
Regards
bibi