C-LeftArrow as backward-word

["pg@gmail.com" <phil.ganchev@gmail.com>]

I want to use control+LeftArrow to move the cursor to the previous
word, and control+RightArrow to move to the next word in Emacs 21
running in xterm. When I press those, I get '5D' and '5C' inserted at
the cursor instead. So I type

M-x global-set-key RET

Then I press Control+LeftArrow, and enter the command 'backward-word'.

But nothing has changed; when I press Control-LeftArrow, I still get
'5D' inserted.

I also tried putting the following in my ~/.emacs, with no effect:

(global-set-key (kbd "M-[ 5 d") 'backward-word)
(global-set-key (kbd "M-[ 5 c") 'forward-word)

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Thanks for your help!