No, that isn't legitimate. A used/required file should always have a package that matches its name. You could export said vars, though.

package includee;

use strict;
use warnings;

use Exporter qw( import );

# I prefer to use `@EXPORT_OK`
# and list the imported things
# in the `use` statement.
our @EXPORT = qw(
   $SHAREDVARIABLE1
   @SHAREDVARIABLE2
   %SHAREDVARIABLE3
   function
);

# Using `use vars` is ok, but dated.
our $SHAREDVARIABLE1;
our @SHAREDVARIABLE2;
our %SHAREDVARIABLE3;

sub function {
  ...
}

1;  # Modules must end with a true value.
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Note that it's usually better to export subs that manipulate the variables rather than exporting the variables themselves. It provides better encapsulation, which has a large number of benefits.

If you want to load a module that's in the same dir as the script, you should add the following to the script:

use FindBin qw( $RealBin );
use lib $RealBin;
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