Could somebody please explain why the following does this?

#! /usr/bin/perl
use warnings;
use strict;
use test();
my $output = testroutine();
print $output, "\n";
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and this has the same result...

#! /usr/bin/perl
use warnings;
use strict;
use test;
my $output = testroutine();
print $output, "\n";
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the result being...

Undefined subroutine &main::testroutine called at ./test.pl line 8.
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If I run the following:

$ perl -e 'map {print $_,"\n"} @INC'
/usr/lib/perl5/5.8/cygwin
/usr/lib/perl5/5.8
/usr/lib/perl5/site_perl/5.8/cygwin
/usr/lib/perl5/site_perl/5.8
/usr/lib/perl5/site_perl/5.8/cygwin
/usr/lib/perl5/site_perl/5.8
/usr/lib/perl5/vendor_perl/5.8/cygwin
/usr/lib/perl5/vendor_perl/5.8
/usr/lib/perl5/vendor_perl/5.8/cygwin
/usr/lib/perl5/vendor_perl/5.8
.
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Now if I alter test.pl to look like:

#! /usr/bin/perl
use warnings;
use strict;
use lib '.'; #My Change
use test();
my $output = testroutine();
print $output, "\n";
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When run, the program outputs the following:

This is a test
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For information test.pm which is in the same directory as test.pm has the following code:

sub testroutine {
        return "This is a test";
}
1;
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Now I may be very ignorant of the use. However, I would expect my first example to work if my second example works. Why would enabling use lib import the module into my namespace? When before I use use lib, '.' is in my @INC. Second, I would think that in actuality both examples should fail since I'm calling test.pm by use test(), I would think this would NOT populate anything into my namespace? I hope this long post makes sense, for I am eager to learn.

Thanks!