It tells the compiler that the second parameter is long, and not just int.
This is necessary in cases where the host language does not have explicit knowledge of the API or the call is not declared manually so that type conversion can occur properly.
Full list sigil , which may be used include the following: generally @and $are not used for API calls.
@= Decimal#= Double (8 bytes)%= Integer (2 bytes)&= Long (4 bytes)!= Single (4 bytes)$= String