Consider:

# file foo
our $foo = 'hello world!';
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#!/usr/bin/perl
use strict;
$\ = "\n";
print "no \$foo" unless defined $main::{foo};
require 'foo'; # or do 'foo'

my $first  = <<'EOH';
print "\$foo defined" if defined $main::{foo};
EOH
eval $first;

my $second = <<'EOH';
print $main::foo;
EOH
eval $second;
__END__
no $foo
$foo defined
hello world!
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and

#!/usr/bin/perl
use strict;
$\ = "\n";
print "no \$foo" unless defined $main::{foo};
require 'foo'; # or do 'foo'
print $main::foo;
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The string evals show that our effectively allocates a symbol table entry for the package. The second example shows that after the compilation phase a symbol table entry main::foo has been allocated.

I think of our as a hybrid beast. It is global in the sense that it generates a global, and a variable declared with our is an alias to the symbol table entry. It is lecical however in that it is transparent to multiple packages in a file.