Difference between uninstalled and deactivated ?

[Chris Jones]

Hi,

I've just noticed something the perhaps someone can explain to me.  
Whenever I run 'sudo port upgrade outpdated', and a port gets  
upgraded, the old port is first deactivated before the new one is  
installed and activated. But the old port is never uninstalled ? What  
does this mean ? Does it mean over time my system will slowly fill up  
with old unused versions of ports ?

  For instance for perl at the moment I have

localhost ~ > sudo port installed | grep perl
Password:
   perl5 @5.8.8_1
   perl5 @5.8.8_2
   perl5 @5.8.9_0 (active)
   perl5.8 @5.8.8_3+darwin_9
   perl5.8 @5.8.9_0
   perl5.8 @5.8.9_1
   perl5.8 @5.8.9_2 (active)


Should I worry about uninstalling the _0 and _1 ports ? If so, is  
there some way I can get this done automatically while upgrading ?

Sorry for the newbie questions ..

Chris