You're correct. Your example gives perl the code ; to execute (i.e. an empty statement; personally I tend to use -e 0 since it accomplishes the same thing and doesn't require quoting to prevent it from being interpreted by the shell). If nothing happens that's good, as it means that the CGI module was found and loaded correctly. Had it not found the module or something blew up you would have instead seen an error (and you could experimentally verify this by trying to load a non-existent module, e.g. perl -MThroatwarbler::Mangrove -e 0).

Update: Erm, anonomonk protestations to the contrary aside, either order works as I said.

$ perl -e 0 -MThroatwarbler::Mangrove
Can't locate Throatwarbler/Mangrove.pm in @INC (@INC contains: /opt/lo
+cal/lib/perl5/site_perl/5.8.9/darwin-2level /opt/local/lib/perl5/site
+_perl/5.8.9 /opt/local/lib/perl5/site_perl /opt/local/lib/perl5/vendo
+r_perl/5.8.9/darwin-2level /opt/local/lib/perl5/vendor_perl/5.8.9 /op
+t/local/lib/perl5/vendor_perl/5.8.8 /opt/local/lib/perl5/vendor_perl/
+5.8.8/darwin-2level /opt/local/lib/perl5/vendor_perl /opt/local/lib/p
+erl5/5.8.9/darwin-2level /opt/local/lib/perl5/5.8.9 .).
BEGIN failed--compilation aborted.
$ perl -MThroatwarbler::Mangrove  -e 0
Can't locate Throatwarbler/Mangrove.pm in @INC (@INC contains: /opt/lo
+cal/lib/perl5/site_perl/5.8.9/darwin-2level /opt/local/lib/perl5/site
+_perl/5.8.9 /opt/local/lib/perl5/site_perl /opt/local/lib/perl5/vendo
+r_perl/5.8.9/darwin-2level /opt/local/lib/perl5/vendor_perl/5.8.9 /op
+t/local/lib/perl5/vendor_perl/5.8.8 /opt/local/lib/perl5/vendor_perl/
+5.8.8/darwin-2level /opt/local/lib/perl5/vendor_perl /opt/local/lib/p
+erl5/5.8.9/darwin-2level /opt/local/lib/perl5/5.8.9 .).
BEGIN failed--compilation aborted.
$ perl -v

This is perl, v5.8.9 built for darwin-2level

Copyright 1987-2008, 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.org/, the Perl Home Pa
+ge.

$ perl5.10.0 -MThroatwarbler::Mangrove -e 0
Can't locate Throatwarbler/Mangrove.pm in @INC (@INC contains: /usr/lo
+cal/lib/perl5/5.10.0/darwin-2level /usr/local/lib/perl5/5.10.0 /usr/l
+ocal/lib/perl5/site_perl/5.10.0/darwin-2level /usr/local/lib/perl5/si
+te_perl/5.10.0 .).
BEGIN failed--compilation aborted.
$ perl5.10.0 -e 0 -MThroatwarbler::Mangrove
Can't locate Throatwarbler/Mangrove.pm in @INC (@INC contains: /usr/lo
+cal/lib/perl5/5.10.0/darwin-2level /usr/local/lib/perl5/5.10.0 /usr/l
+ocal/lib/perl5/site_perl/5.10.0/darwin-2level /usr/local/lib/perl5/si
+te_perl/5.10.0 .).
BEGIN failed--compilation aborted.
$ perl5.10.0 -e 0 -MCGI
$ perl5.10.0 -MCGI -e 0
$
[download]

Not in his case, in his case -MCGI is the first argument to the ; program (; being the first argument to the -e switch)

-e does not end the processing of the options.

$ perl -e'print "a\n";' -e'print "b\n";'
a
b
[download]

And an example with -M:

$ perl -e'print "a\n";' -e'print "b\n";' -MO=Deparse
print "a\n";
print "b\n";
-e syntax OK
[download]

Actually yes, to get perl to stop processing switches after -e you need to use --,

$ perl -le"print for @ARGV, keys %INC " -MCGI -- -MCGI
-MCGI
warnings/register.pm
Carp.pm
vars.pm
strict.pm
Exporter.pm
constant.pm
warnings.pm
CGI/Util.pm
overload.pm
CGI.pm
[download]

Many thanks

It's a minor savings but I do find myself typing this kind of thing a fair amount (I have a couple versions aliases too) so I suggest it-

There are other useful switches for testing. See the switches section in perlrun for enough options to make your head explode.

moo@cow>perl -MCGI -we'print'
Use of uninitialized value in print at -e line 1.
[download]

See perlintro, perlrun