invalid command name "toplevel"
    while executing
"toplevel .t1"
    (in namespace eval "::request" script line 3)
    invoked from within
"namespace eval ::request $script"
    ("::try" body line 12)
OUTPUT BUFFER:
#!/usr/local/bin/wish

toplevel .t1
pack [button .t1.b -bg cyan -text " B1 " -command [list raise .t2]]

toplevel .t2
pack [button .t2.b -bg green -text " B2 " -command [list raise .t3]]

toplevel .t3
pack [button .t3.b -bg yellow -text " B3 " -command [list raise .t1]]