abusing prototype() for API version

can-ver.pl

# if ($obj->can('foo')) { ... }

# if ($obj->can('foo', $api_version)) { ... }

# if ($obj->can('foo', $api_version, $minor_version)) { ... }

use strict;
use Number::Nary qw(n_codec);

my $major = 10;
my $minor = 5;

my ($enc, $dec) = n_codec('$@%');

my $mj = $enc->($major);
my $mn = $enc->($minor);

prototype($sub) = ($major . ';' . $minor);