Raccoon <- yap.. russian chars is in the 256 ascii table..
shoot <- here is a scripted alternative.. It will work correctly with the russian chars and with latin chars for other it will return $false.
Code:
/*
$chr(192) - &amp;#1040;
$chr(223) - &amp;#1071;
$chr(224) - &amp;#1072;
$chr(255) - &amp;#1103;
syntax: $IsUpperFixed(Char)
*/
Alias IsUpperFixed {
  var %asc = $asc($1)
  if ((%asc &gt;= 192) &amp;&amp; (%asc &lt;= 223)) return $true
  elseif ((%asc &gt;= 65) &amp;&amp; (%asc &lt;= 90)) return $true
  else return $false
}

;syntax: $IsLowerFixed(Char)
Alias IsLowerFixed {
  var %asc = $asc($1)
  if ((%asc &gt;= 224) &amp;&amp; (%asc &lt;= 255)) return $true
  elseif ((%asc &gt;= 97) &amp;&amp; (%asc &lt;= 122)) return $true
  else return $false
}

mIRC Chm Help 6.16.0.3 Full Anchored!