How do i save a XML to variable or table that is produced by SQL saved procedure?

Here's my sample:

DECLARE @ReportResultXml TABLE(RXml XML)    
DECLARE @ResultXml  XML = NULL

INSERT @ReportResultXml EXEC (@Script + ' FOR XML RAW, ROOT, XMLSCHEMA, ELEMENTS')
SELECT @ResultXml = RXml FROM @ReportResultXml
EXEC Repor.ProcInsert 1, @ResultXml

SELECT @ResultXml

@Script consists of SQL query:

DECLARE @PeriodID INT
SET @PeriodID = 12
SELECT TOP 10 PeriodID, Name
FROM Agent.Points
WHERE PeriodID = @PeriodID

Above statement will generate following alert:

The FOR XML clause isn't permitted inside a Place statement.

This will let you to locate your solution:

declare @script nvarchar(max)
set @script = 'select 1 as a, 2 as b for xml raw'

declare @ReportResultXml table (RXml XML)
declare @ResultXml xml

declare @sql nvarchar(max)

set @sql = 'set @ResultXml = (' + @script + ')'
execute sp_ExecuteSQL @sql, N'@ResultXml xml output', @ResultXml output

insert into @ReportResultXml select @ResultXml

select * from @ReportResultXml