Reorganize Index

DECLARE @strIndex_Name varchar(50)
DECLARE @strTable_Name varchar(50)

SET @strTable_Name = 'DIM_AR_CLASS'
SET @strIndex_Name = 'IX_DIM_AR_CLASS_1'

PRINT @strTable_Name
PRINT @strIndex_Name

ALTER INDEX @strTable_Name ON @strIndex_Name REORGANIZE


Result msg:

DIM_AR_CLASS
IX_DIM_AR_CLASS_1
Msg 102, Level 15, State 1, Line 12
Incorrect syntax near '@strTable_Name'.

If i change the statement as below then it work fine.
ALTER INDEX IX_DIM_AR_CLASS_1 ON DIM_AR_CLASS
REORGANIZE

Anyone know why ?Does this alter index statement not support variable during execution time?
Appreciate any help.
Thanks.