SQL Server Scalar UDF inline

hi, here is a demo version of the function and the sample call to it with output

-- function used to get value for a key
CREATE FUNCTION [dbo].[fn_ForDemo] (@mSettings NVARCHAR(1000),
@mKey NVARCHAR(100))
RETURNS NVARCHAR(100)
AS
BEGIN
DECLARE @mValue NVARCHAR(100)
DECLARE @mKeyValue NVARCHAR(200)

IF @mSettings IS NULL OR @mKey IS NULL
BEGIN
SET @mValue = NULL
END
ELSE
BEGIN
SELECT @mKeyValue = VALUE
FROM STRING_SPLIT(@mSettings, ';')
WHERE VALUE LIKE '%' + @mKey + '|:|%'

SELECT @mValue = Value
FROM STRING_SPLIT(@mKeyValue, ':')

IF @mValue LIKE '|%'
SET @mValue = SUBSTRING(@mValue, 2, LEN(@mValue) - 1)

IF @mValue LIKE '%|'
SET @mValue = SUBSTRING(@mValue, 1, LEN(@mValue) - 1)
END

RETURN COALESCE(@mValue, '')
END
GO

SELECT dbo.fn_ForDemo('abc|:|123|;|def|:|345|;|ghy|:|678|;|jkl|:|999|;|mno|:|888'
,'jkl')
--output= jkl(incorrect)


SELECT dbo.fn_ForDemo('abc|:|123|;|def|:|345|;|ghy|:|678|;|jkl|:|999|;|mno|:|888'
,'jkl')
OPTION (USE HINT('DISABLE_TSQL_SCALAR_UDF_INLINING'))
--output= 999 (correct)