average congestion window

I have to repeat a NS2 simulation a number of times, each time changing the number of network nodes, and calculate the average congestion window. Tcl script creates a file named “winfile” after the execution, in which the first column is the time, the second the value of the congestion window. I wrote a perl script to implement this:

$sum=0;

$average=0;

$j=0;



for($i=2; $i<=10;$i++){



system  ("ns tesina.tcl $i");



open (DATA,"<$winfile")

|| die "Can't open $winfile $!";





while () {

@x=split(' ');

$sum=$sum+$x[1];

$j++;



}

$average=$sum/$j;

print STDOUT "$i $averagen";

$sum=0;

$average=0;

$j=0;



}

close DATA;

exit(0);

but when I run it tells me can not open the file, despite being created from the execution of the tcl files. By modifying the file in this way

$infile=argv[0];

...

it works. but I always get the same average value, which is impossible. It seems that the script does not run tcl but analyze a file previously created.
how can I fix that?