% perl -MData::Dumper -Mstrict -we 'my %h; $h{"foo", ("")x$_} = $_ for 0..4; print Dumper \%h'
$VAR1 = {
'foo' => 3,
'foo' => 1,
'foo' => 2,
'foo' => 4,
'foo' => 0,
};

何コレおもしろい