A problem with variable

[Leslie Jensen]

I've defined a variable

proxyport = "{ 8080 }"

The rule

rdr on $int_if inet proto tcp from $internal_net to any /
port $proxy_services -> $proxy port $proxyport

gives me a "Syntax error in config file:"

I use the same variable in another rule and it does not produce a 
"Syntax error"

pass in on $int_if inet proto tcp from $internal_net to /
$proxy port $proxyport keep state

If I change the variable in the first rule to 8080 it works.

Can someone shed some light on this?

Thanks

/Leslie