Removing installed packages

[Hall Stevenson <hallstevenson@mindspring.com>]

I was looking at what packages I've installed over time, along with ones
installed by default, and am going to some cleaning. In doing so, I ran
across a couple that I want to ask about...

They are:

perl
perl-5.005
perl-5.005-base
perl-5.6
perl-5.6-base
perl-base   

and 

tcl8.0
tcl8.2
tcl8.2-dev
tcl8.3
tcl8.3-dev

The 'dev' packages for tcl don't concern me. I'll remove the related one
when I figure out what's going on.

Why, for example, are there two versions of perl ?? Isn't perl-5.6
backwards-compatible with perl-5.0x ?? I do see that the perl-5.6
package can be removed and will leave me with 'perl'.

I assume tcl is similar.

Thanks in advance
Hall