INTRODUCTION
This typofix.pl is based on the original one, available from 
irssi.org/scripts/new.

FEATURES
I've changed it, adding these features:

* Handles s!!!, s%%% etc, so a "/" can be substituted with s|/|Blah|
* Handles the /i (case insensitivity) modifier
* Leaves the old text in place, but in another color
  - If you like the old behaviour: /set typofix_format new
* Handles \1 .. \8 and $1 .. $8
* Doesn't crash on invalid regexes (sigh, that should have been wrapped 
  in an eval BLOCK for ages)
* Handles escapes, so a "/" can be substituted with s/\//Blah/
  - Irssi uses slashes internally, so this could screw things up if you
    use colors
* Handles optional leading whitespace
* Handles the ^-anchor (^ matches the null-string at the beginning of a 
  line

Patches are NOT incremental

CHANGES
J1..J5 - DO NOT USE. Contain a nasty endless-loop bug
J6     - Fixed endless-loop bug, improved ^-anchor
J7     - Set limit back to 5 (typofix_limit)
       - Added setting typofix_feature_string (heh)
       - Changed typofix_modify_string default to a nullstring.

BUGS
* Irssi wants to write its next line after the replaced one, so
<> Foo
<> s/F/B/
<> s/oo/ar/
would be printed as:
<> FBooar (but with Bar in bold, Foo in gray)
<> s/oo/ar/
<> s/F/B/
This, I can live with - but Irssi doesn't redraw correctly, so you'll 
have to press ^L or scroll up and down. I discovered that adding 
another line helps. That, in fact, is a feature, not a bug.