$ cat MyClass.pm

##</code><code>##

use strict;
use warnings;

package MyClass {
    use parent 'Exporter';
    our @EXPORT = 'foo';

    sub foo { 42 }
};

1;

##</code><code>##

$ cat script.pl

##</code><code>##

use lib '.';
use MyClass;

$bar = foo;

print "$bar\n";

##</code><code>##

$ perl script.pl

##</code><code>##

42

##</code><code>##

$ cat MyClass2.pm

##</code><code>##

use strict;
use warnings;

package MyClass2 {
    use parent 'Exporter';
    our @EXPORT = 'foo';

    use Import::Into;
    strict->import::into(1);

    sub foo { 42 }
};

1;

##</code><code>##

$ cat script2.pl

##</code><code>##

use lib '.';
use MyClass2;

$bar = foo;

print "$bar\n";

##</code><code>##

$ perl script2.pl

##</code><code>##

Global symbol "$bar" requires explicit package name (did you forget to declare "my $bar"?) at script2.pl line 4.
Global symbol "$bar" requires explicit package name (did you forget to declare "my $bar"?) at script2.pl line 6.
Execution of script2.pl aborted due to compilation errors.