multiple versions of a package?

[Gábor Farkas]

hi,

while using macports, i found this problem that i'm not able to solve:


===============================================
omoikane:~ gabor$ port installed subversion
The following ports are currently installed:
   subversion @1.4.2_0
   subversion @1.4.3_0
   subversion @1.4.3_1 (active)


omoikane:~ gabor$ sudo port uninstall subversion @1.4.2_0
--->  Unable to uninstall subversion 1.4.2_0, the following ports depend 
on it:
--->    subversion-perlbindings
Error: port uninstall failed: Please uninstall the ports that depend on 
subversion first.
omoikane:~ gabor$ sudo port uninstall subversion @1.4.3_0
--->  Unable to uninstall subversion 1.4.3_0, the following ports depend 
on it:
--->    subversion-perlbindings
Error: port uninstall failed: Please uninstall the ports that depend on 
subversion first.
omoikane:~ gabor$ sudo port uninstall subversion @1.4.3_1
--->  Unable to uninstall subversion 1.4.3_1, the following ports depend 
on it:
--->    subversion-perlbindings
Error: port uninstall failed: Please uninstall the ports that depend on 
subversion first.
=================================================

so, my questions are:

1. why do i have multiple versions of 'subversion' installed? when i do 
'port upgrade subversion', i assumed it installs the new version and 
removes the old one... is that so?

2. from the messages above, on what does 'subversion-perlbindings' 
depend exactly? on a specific version of 'subversion'? or simply on 
'subversion' as a package?


i have used several package managers in the past (rpm, debian, 
gentoo..), but macports's behavior seems to be quite different. i'd like 
to understand it, so could you please explain to me what's happening there?

thanks,
gabor