I'm using a discrete event simulator called ns-2 that was built using Tcl and C++. I was trying to write some code in TCL:

set ns [new Simulator]

set state 0

$ns at 0.0 "puts \"At 0.0 value of state is: $state\""
$ns at 1.0 "changeVal"
$ns at 2.0 "puts \"At 2.0 values of state is: $state\""

proc changeVal {} {
    global state
    global ns
    $ns at-now "set state [expr $state+1]"
    puts "Changed value of state to $state"
}

$ns run

Here's the output:

At 0.0 value of state is: 0
Changed value of state to 0
At 2.0 values of state is: 0

The value of state does not seem to change. I am not sure if I am doing something wrong in using TCL. Anyone has an idea as to what might be going wrong here?

EDIT: Thanks for the help. Actually, ns-2 is something over which I do not have much control (unless I recompile the simulator itself). I tried out the suggestions and here's the output:

for the code:

set ns [new Simulator]

set state 0

$ns at 0.0 "puts \"At 0.0 value of state is: $state\""
$ns at 1.0 "changeVal"
$ns at 9.0 "puts \"At 2.0 values of state is: $state\""

proc changeVal {} {
    global ns
    set ::state [expr {$::state+1}]
    $ns at-now "puts \"At [$ns now] changed value of state to $::state\""
}

$ns run

the output is:

At 0.0 value of state is: 0
At 1 changed value of state to 1
At 2.0 values of state is: 0

And for the code:

set ns [new Simulator]

set state 0

$ns at 0.0 "puts \"At 0.0 value of state is: $state\""
$ns at 1.0 "changeVal"
$ns at 9.0 "puts \"At 2.0 values of state is: $state\""

proc changeVal {} {
    global ns
    set ::state [expr {$::state+1}]
    $ns at 1.0 {puts "At 1.0 values of state is: $::state"}
}

$ns run

the output is:

At 0.0 value of state is: 0
At 1.0 values of state is: 1
At 2.0 values of state is: 0

Doesn't seem to work... Not sure if its a problem with ns2 or my code...