package FooConfig;

use strict;

[ constructor and some functions ]

sub important_func
{
 my $self = shift;
 my $arg = shift;

 my %hash =
 (
  '1' => 'red',
  '2' => 'blue',
  '3' => 'green',
 )

 return $hash{ $arg } if $hash{ $arg };
}

##</code><code>##

package Foo;

use strict;

[ constructor and some functions ]

sub somesub_foo
{
 my $self = shift;

 [...]
 use FooConfig;
 my $FooConfig = FooConfig->new;

 my $ref = \&FooConfig->important_func( '1' );

 [ do something with this ]
}