package L10N;
use base qw(Locale::Maketext);
1;

package L10N::pl;
use Locale::Maketext;
use base qw(L10N);
%Lexicon = (
    "Foobar [quant,_1,staff]" => "Foobar [quant,_1,staf,stafow,zero stafu]\n",
    "Foobar [_1]" => "Foobar [quant,_1,staf,stafow,zero stafu]\n",
);
                                                                       1;

package Main;

my $lh = L10N->get_handle('pl') || die "Language?";
print $lh->maketext("Foobar [_1]", 2);
print $lh->maketext("Foobar [quant,_1,stuff]", 2);

__OUTPUT__
Foobar 2 stafow
maketext doesn't know how to say:
Foobar [quant,_1,stuff]
as needed at a1.txt line 20

##</code><code>##

While you can use arbitrary unique IDs for lexicon keys (like "_min_larger_max_error"), it is often useful for if an entry's key is itself a valid value,