Variable Interpolation not working for me.

[Anthony_Crouch]

I am currently trying to test out the variable Interpolation  and cannot
get it to work properly. I am not sure if it is bug or just misuse on my
part as I am new to the commons package. Any help would be much
appreciated. 

I load up my configuation files this way and all else seems to work. 

                        config = new
PropertiesConfiguration(pathfilename);
                        FileChangedReloadingStrategy strat = new
FileChangedReloadingStrategy();
                        strat.setRefreshDelay(30000);
                        config.setReloadingStrategy(strat);

My property exists in my main propery file that I use to load other
property files. 

include = General.properties
include = DragonfxBeanPoolFactory.properties
include = MsgEventMapping.properties
include = LSPMsgTypeMappings.properties
include = ReportConfig.properties
include = SendingMessage.properties
LOGFILE_PROPERTIES={sys:app_env}_{sys:app_vm}_log4j.xml

My system properties are set using the vm parameter.  -Dapp_env=dev
-Dapp_vm=web 

They are available when I use system.getProperty to access them. I am
using 1.4 version of the commons jar. 

When I get the property it returns the string with the brackets etc like
it cannot find the system property. 

Thanks ahead of time for any help you may provide.