[features request] String transformation in replacement

[nebuchadnezzar]

Hello,

This is a features request, I apologies if it's not the good place to post it.

I want to make some string transformation during a replacement, I make
a match with \(...\) and want to lowercase the corresponding \1 in the
replacement.

I search in the emacs manual and elisp reference manual before asking
on #emacs, it seems that there is no solution.

What I search to do is like the \L in perl.

Regards.

In GNU Emacs 22.0.50.1 (i486-pc-linux-gnu, X toolkit, Xaw3d scroll bars, 
multi-tty)
 of 2005-06-27 on walrus, provided by address@hidden
configured using `configure '--build' 'i486-linux-gnu' '--host' 
'i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' 
'--libexecdir=/usr/lib' '--localstatedir=/var' '--infodir=/usr/share/info' 
'--mandir=/usr/share/man' '--with-pop=yes' '--with-gif' '--enable-asserts' 
'--with-x=yes' '--with-x-toolkit=athena' '--with-toolkit-scroll-bars' 
'CC=gcc-3.4' 'CFLAGS=-DDEBIAN -g -fno-crossjumping -O2' 
'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: address@hidden
  locale-coding-system: iso-8859-15
  default-enable-multibyte-characters: t

Major mode: Text

Minor modes in effect:
  erc-log-mode: t
  erc-services-mode: t
  erc-autojoin-mode: t
  erc-button-mode: t
  erc-ring-mode: t
  erc-pcomplete-mode: t
  erc-track-mode: t
  erc-fill-mode: t
  erc-stamp-mode: t
  erc-netsplit-mode: t
  erc-smiley-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  display-time-mode: t
  mouse-wheel-mode: t
  delete-selection-mode: t
  auto-compression-mode: t
  menu-bar-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  next-error-follow-minor-mode:  Fol

Recent input:
e SPC : - ) ESC O D ESC O D ESC O D ESC O D s RET d 
f DEL DEL M-x e m TAB a TAB b u TAB DEL DEL DEL DEL 
DEL DEL DEL DEL b u TAB C-g M-x a p r o TAB RET b u 
g RET C-x o C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n 
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n 
C-n C-n C-n C-v C-v C-v C-v C-v C-x k RET M-x r e p 
o TAB r TAB RET

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