cleft and cright don't backward_word nor forward_word

Binary package hint: irssi

I type some words, then I try to go backwards (in the line in irssi) word by word, and instead of going backwards one word, it prints "5D". Same stands for trying to go forward in the line in irssi

I'm using:
Irssi version 0.8.10-2ubuntu1
Ubuntu feisty fawn (7.04) beta
bash
gnome terminal
screen (screen -S irc irssi)
a standard keyboard (en-US language)

There are some bindings in irssi, like meta-b and meta-f (that is, alt-b and alt-f), which do the same thing as cleft and cright, but meta-b and meta-f work OK.

I've tried adding:
/bind 5D backward_word
/bind 5C forward_word
..in irssi and it works, but when i type "5D" (not press ctrl-left, simply type), it too does backword_word,whereas "5C" does forward_word.

In bash/gnome terminal editing a line works well (forward-word and backward-word are OK there).

I do not have a ~/.inputrc file, just the /etc/inputrc which is the following:
(PASTE START)

# /etc/inputrc - global inputrc for libreadline
# See readline(3readline) and `info rluserman' for more information.

# Be 8 bit clean.
set input-meta on
set output-meta on

# To allow the use of 8bit-characters like the german umlauts, comment out
# the line below. However this makes the meta key not work as a meta key,
# which is annoying to those which don't need to type in 8-bit characters.

# set convert-meta off

# try to enable the application keypad when it is called. Some systems
# need this to enable the arrow keys.
# set enable-keypad on

# see /usr/share/doc/bash/inputrc.arrows for other codes of arrow keys

# do not bell on tab-completion
# set bell-style none
# set bell-style visible

# some defaults / modifications for the emacs mode
$if mode=emacs

# allow the use of the Home/End keys
"\e[1~": beginning-of-line
"\e[4~": end-of-line

# allow the use of the Delete/Insert keys
"\e[3~": delete-char
"\e[2~": quoted-insert

# mappings for "page up" and "page down" to step to the beginning/end
# of the history
# "\e[5~": beginning-of-history
# "\e[6~": end-of-history

# alternate mappings for "page up" and "page down" to search the history
# "\e[5~": history-search-backward
# "\e[6~": history-search-forward

# mappings for Ctrl-left-arrow and Ctrl-right-arrow for word moving
"\e[1;5C": forward-word
"\e[1;5D": backward-word
"\e[5C": forward-word
"\e[5D": backward-word
"\e\e[C": forward-word
"\e\e[D": backward-word
"\e5C": forward-word
"\e5D": backward-word

$if term=rxvt
"\e[8~": end-of-line
"\eOc": forward-word
"\eOd": backward-word
$endif

# for non RH/Debian xterm, can't hurt for RH/Debian xterm
# "\eOH": beginning-of-line
# "\eOF": end-of-line

# for freebsd console
# "\e[H": beginning-of-line
# "\e[F": end-of-line

$endif

(PASTE END)