Cleaning up port dependencies

[Nick Kraal]

Dear all,

Running 'portupgrade -a' religiously to automatically update all 
installed installed ports, I have started to notice duplicates in 
certain installed applications. Most likely due to dependencies.

%pkg_info
...
ruby-1.6.8.2004.07.28 An object-oriented interpreted scripting language
ruby-1.8.2.p2_1       An object-oriented interpreted scripting language
tk-8.3.5_5          Graphical toolkit for TCL
tk-8.4.7,2          Graphical toolkit for TCL
libtool-1.3.5_2     Generic shared library support script (version 1.3)
libtool-1.5.10      Generic shared library support script (version 1.5)

Is there a way to check on whether dependencies on the earlier version 
still exist. Or perhaps I have deleted a port that does not need that 
port version any more. Just some housekeeping here.

Thanks in advance,

-nick/