Stored procedure recieves to much data after change in DB

In our sales database we import data from an external source. They have done some changes and the sales period now looks like this: 

 - 0113_AU
 - 0113_DK
 - 0113_EU
 - 0114_AU
 - 0214_EU
etc....

The problem is that i only want to fetch one period, example all sales for: 0113. But when i run my stored procedure now, it fetches all data when i write 0113. Here is the beginning and end of my procedure.

                 @period nvarchar

and 

                 sales.period_year_region = @period

How can i edit the last part so it fetches only for the periods that has 0113, and nothing else? Even when i write 0113_EU it receives to much data...