use constant 
    {
        MY_CONSTANT1 => 1,
        MY_CONSTANT2 => 2,
        MY_CONSTANT3 => 3,
        MY_CONSTANT4 => 4
    };

sub useConstants
{
   #able to use constants fine in here...
   my $var = MY_CONSTANT4;
   print "$var\n"; #outputs '4'
}

1;