Code:

proc mirc2html str {   set re {([\002\017\026\037]|[\003]{1}[0-9]{0,2}[\,]{0,1}[0-9]{0,2})}array   set colors { 0 white   1 black    2 navy    3 green                4 red     5 maroon   6 purple  7 olive                8 yellow  9 lime    10 teal   11 aqua               12 blue   13 fuchsia 14 gray   15 silver}   set numtags 0; set bold 0   while {[regexp -indices $re $str -> idxs]} {      set b [lindex $idxs 0]      set e [lindex $idxs 1]      set sub [string range $str $b $e]      switch [string index $sub 0] {         "\002" {            if !$bold {               set tag "<span style=\"font-weight:bold\">"               set bold 1            } {               set tag "<span style=\"font-weight:normal\">"               set bold 0            }            incr numtags         }         "\017" {            set tag [string repeat "</span>" $numtags]            set numtags 0         }         "\026" {            set tag [string repeat "</span>" $numtags]                        append tag "<span style=\"color:white;background-color:black\">"            set numtags 1         }         "\037" {            set tag "<span style=\"text-decoration:underline\">"            incr numtags         }         "\003" {            set fg [lindex [split [string range $sub 1 e] ,] 0]            set bg [lindex [split [string range $sub 1 e] ,] 1]            if {$fg != "" || $bg != ""} {               if {$fg > 15 || $bg > 15} {                  set tag "<span>"               } elseif {$fg != "" && $bg != ""} {                  set tag "<span style=\"color:$colors($fg);background-color:$colors($bg)\">"               } elseif {$fg != "" && $bg == ""} {                  set tag "<span style=\"color:$colors($fg)\">"               } else {                  set tag "<span style=\"background-color:$colors($bg)\">"               }               incr numtags            } {               set tag [string repeat "</span>" $numtags]               set numtags 0            }         }      }      set str [string replace $str $b $e $tag]   }   append str [string repeat "</span>" $numtags]   return $str}