perl tk.pl          & rem ok
tk.pl               & rem ok
start perl tk.pl    & rem ok
start tk.pl         & rem ok
start /b perl tk.pl & rem requires second ENTER, it is the start /b option that's confusing things
start /b tk.pl      & rem requires second ENTER, same culprit

##</code><code>##

start /b wperl tk.pl & rem does not require second ENTER
wperl tk.pl          & rem does not require start/b and doesn't require a cmd.exe window to be created, even when run from Run dialog or from a file association

##</code><code>##

start /b perl tk.pl & rem no longer requires second ENTER after registry fix
start /b tk.pl      & rem no longer requires second ENTER after registry fix