package Example::Package;

use strict;
use warnings;
use Data::Dumper;

use constant foo => 1;

BEGIN {
    no strict 'refs';
    my %subs = map {$_ => 1} grep *{$_}{CODE},
      keys %{__PACKAGE__ . '::'};
    
    sub added_subs () {
        grep *{$_}{CODE} && !$subs{$_},
          keys %{__PACKAGE__ . '::'};
    }
}

use constant { bar => 2, baz => 3 };

print Dumper [added_subs];

__END__