perlbrew switch perl-5.18.2 opening subshell

Apologies in advance if this is the wrong place to post.

I am setting up a new machine with Linux/Ubuntu v13.10 -- the first time 
in nearly two years when I am using Linux as a desktop.  I'm trying to 
make a clean start with respect to my Perl-related programming practices:

* I want to use perlbrew as much as possible
* I want to use cpanm rather than cpan as much as possible

But I am having a hell of a time trying to get perlbrew to work in the 
way I am accustomed to it working on my $job MacBook Pro.

I have (several times today) installed perlbrew with this command:

cpan
 > install App::perlbrew

I now have:

#####
which perlbrew
/usr/local/bin/perlbrew
#####

And I have added: 'source ~/perl5/perlbrew/etc/bashrc' to the end of my 
~/.bash_profile file.  (AAMOF, it's the only entry yet in that file.)

And I have said: 'perlbrew init'

The following commands work as expected:

#####
perlbrew available
perlbrew install perl-5.18.2
perlbrew list
#####

However, whenever I say:

######
perlbrew switch perl-5.18.2
######

I get:

#####
A sub-shell is launched with perl-5.18.2 as the activated perl. Run 
'exit' to finish it.

bash-4.2$
#####

This is unexpected and undesired behavior.  On the basis of using 
perlbrew on my work laptop for > 1 year, I would *not* expect a 
sub-shell to be opened.  I would expect that, from the moment of 
'perlbrew switch' forward, I would:

a) stay in the same shell
b) have 'perl -v' point to the 5.18.2 underneath my homedir.

On this new machine, when I am in the subshell, which perl -v gives 
5.18.2.  But when I exit, I'm back to the vendor perl.

'perldoc perlbrew' documents 'switch' as: Permanently use the specified 
per as default.

That's the behavior I want.  I don't want a subshell to be opened.  I 
want perlbrew switch perl-5.18.2 to make 5.18.2 my default perl.

Can anyone tell me what I'm doing wrong?

Thank you very much.
Jim Keenan