As gellyfish said, you can have multiple perls installed simultaneously:

$ perl -v

This is perl, v5.8.0 built for i386-linux-thread-multi
(with 1 registered patch, see perl -V for more detail)

Copyright 1987-2002, Larry Wall

Perl may be copied only under the terms of either the Artistic License
+ or the
GNU General Public License, which may be found in the Perl 5 source ki
+t.

Complete documentation for Perl, including FAQ lists, should be found 
+on
this system using `man perl' or `perldoc perl'.  If you have access to
+ the
Internet, point your browser at http://www.perl.com/, the Perl Home Pa
+ge.

$ perl5.8 -v

This is perl, v5.8.6 built for i686-linux

Copyright 1987-2004, Larry Wall

Perl may be copied only under the terms of either the Artistic License
+ or the
GNU General Public License, which may be found in the Perl 5 source ki
+t.

Complete documentation for Perl, including FAQ lists, should be found 
+on
this system using `man perl' or `perldoc perl'.  If you have access to
+ the
Internet, point your browser at http://www.perl.com/, the Perl Home Pa
+ge.

$ p58 # change environment
$ perl5.8.3 -v

This is perl, v5.8.3 built for i686-linux

Copyright 1987-2003, Larry Wall

Perl may be copied only under the terms of either the Artistic License
+ or the
GNU General Public License, which may be found in the Perl 5 source ki
+t.

Complete documentation for Perl, including FAQ lists, should be found 
+on
this system using `man perl' or `perldoc perl'.  If you have access to
+ the
Internet, point your browser at http://www.perl.com/, the Perl Home Pa
+ge.
[download]

Note - I have 5.8.4 and 5.8.5 installed as well. Except for 5.8.0, they inherit each others' modules, as well. 5.8.0 is what comes with RHEL3, which I leave as-is so that RHEL3 apps continue to work, while the rest were compiled into a new directory, /share/perl5, and are what I use for my own code. Before I upgraded to RHEL3, I had RH7.3, which had Perl 5.6, and I also had compiled 5.8.0, and 5.8.1.

As to "start developpement with 5.0" - that's not quite what you're doing. Between 5.005 and 5.6, Perl renamed its numbering scheme a bit. 5.005 in the old scheme is the same as 5.5 in the new scheme. Which is significantly newer than 5.0 ;-)

Update: After re-reading the output, I realised that I hadn't updated my perl5.8 symlink to the latest perl version. Corrected the output above.