Is there StartsWith or Contains in t sql with variables?

It seems like what you want is http://msdn.microsoft.com/en-us/library/ms186323.aspx.

In your example it would be (starts with):

set @isExpress = (CharIndex('Express Edition', @edition) = 1)

Or contains

set @isExpress = (CharIndex('Express Edition', @edition) >= 1)

StartsWith

a) left(@edition, 15) = 'Express Edition'
b) charindex('Express Edition', @edition) = 1

Contains

charindex('Express Edition', @edition) >= 1

Examples

left function

set @isExpress = case when left(@edition, 15) = 'Express Edition' then 1 else 0 end

iif function (starting with SQL Server 2012)

set @isExpress = iif(left(@edition, 15) = 'Express Edition', 1, 0);

charindex function

set @isExpress = iif(charindex('Express Edition', @edition) = 1, 1, 0);

I would use

like 'Express Edition%'

Example:

DECLARE @edition varchar(50); 
set @edition = cast((select SERVERPROPERTY ('edition')) as varchar)

DECLARE @isExpress bit
if @edition like 'Express Edition%'
    set @isExpress = 1;
else
    set @isExpress = 0;

print @isExpress