Perl "Constants"

[zerohero]

I'd like to have read-only constants which exist in a module that I include. The purpose of the constant is to eliminate "magic numbers", as one would do with a #define in C.

What I've been doing, which has some drawbacks, is to make a module with Exporter and do the following, and then import each constant into the package it's used in.

package MyConstants;
use base qw (Exporter);

our @EXPORT_OK =
qw (SOME_CONSTANT);                                      
                                                                      
+         
use constant SOME_CONSTANT => 'the value';

Is there a better method than this? This suffers the drawback that inside of a hash, it doesn't get interpolated (i.e. $h{SOME_CONSTANT} doesn't behave as one would "like").