The [exec] command treats ampersands in its arguments specially, e.g. for making execution asynchronous. This can be a problem if an argument, like an URL, contains ampersamds.

petterik@gol.com (Petteri K) writes in [the comp.lang.tcl newsgroup]:

 Would anybody know a workaround in case $url contains
 character '&' e.g. 
 http://127.0.0.1/cgi-bin/script?var1=abc&var2=xyz
[Benjamin Riefenstahl] replied:
[exec] plays tricks with quoting which make it impossible for me to
get the right command executed in Tcl 8.3.4.  What works on W2K here
though is this:

   set url "http://www.tcl.tk?hello&hi"
   set shell [open "|[file join $env(COMSPEC)]" w]
   fconfigure $shell -buffering line
   puts $shell "start \"\" \"$url\""
   puts $shell exit
   close $shell

I hope this works on Windows 9x/Me, too.