Slightly modified synopsis of Term::TermKey::Async:

use strictures;
use Term::TermKey::Async qw(FORMAT_VIM KEYMOD_CTRL);
use IO::Async::Loop;
use Time::HiRes qw(time);
binmode STDOUT, ':encoding(UTF-8)';

my $loop = IO::Async::Loop->new;
my $tka = Term::TermKey::Async->new(
    term => \*STDIN,
    on_key => sub {
        my ($self, $key) = @_;
        printf "Got key: %.8f %s\n", time, $self->format_key($key, FOR
+MAT_VIM);
        $loop->loop_stop if $key->type_is_unicode and $key->utf8 eq "C
+" and $key->modifiers & KEYMOD_CTRL;
    },
);
$loop->add($tka);
$loop->loop_forever;
[download]

Output:

$ perl termkey.pl
Got key: 1338309112.93089604 我
Got key: 1338309112.93100500 喜
Got key: 1338309112.93102598 欢
Got key: 1338309115.18962908 吃
Got key: 1338309116.35776711 冰
Got key: 1338309116.35783195 淇
Got key: 1338309116.35785198 淋
Got key: 1338309116.78892303 。

You can see clearly from the timestamps how I grouped the words/phrases in the input method editor. Only once a phrase is complete in the IME, it is passed off to the terminal.

I haven't tested this on Windows.