Am I overthinking?

EDIT: No, I'm undertesting.

DECLARE@Searchedchar(1),

@Newchar(1)

SET @Searched = 'L'

SET @New = 'M'

DECLARE @test-2TABLE(

stringvarchar(1000))

INSERT @test-2

SELECT 'L@*K@*H@/324' AS string

UNION ALL SELECT '(AF#-AR#)*(Y#+BB#)'

UNION ALL SELECT 'TT#*(L#+D@)*L@'

UNION ALL SELECT '((AE#-AR#)*(Y#+A#))/Y#';

WITH cteTally(n) AS ( SELECT TOP 1000 ROW_NUMBER() OVER( Order BY (SELECT NULL)) FROM master.sys.all_columns),

Data AS(

SELECT '+' + string string, n, SUBSTRING( '+' + string, n, 1) ch

FROM @test-2, cteTally)

UPDATE t SET string = STUFF( REPLACE( d.string, dp.ch+d.ch+dn.ch, dp.ch+@New+dn.ch),1,1,'')

FROM @test-2 t

JOIN Data d ON '+' + t.string = d.string

JOIN Data dp ON d.string = dp.string

AND d.n-1 = dp.n

AND dp.ch LIKE '[^A-Z]'

JOIN Data dn ON d.string = dn.string

AND d.n+1 = dn.n

AND dn.ch IN ( '#', '@', '&')

WHERE d.ch = @Searched

SELECT * FROM @test-2