For most practical purposes, you can treat a namespace exactly as if it were a hash.

sub capsule {
    my($capsule_name, $file) = @_;
    my $src = slurp $file;
    eval "package $capsule_name; \n#line 1\n$src" or die $@;
}

[...]

capusle("Foo", "foo.pl");

print $Foo::{text};
[download]

An alternative is to load everything into a dummy package with a throwaway name, then to export everything out of it. Of course, both these proposals break if foo.pl switches namespaces itself, and that's hard to catch.