For example:
100 2
-2  44
150 9
26  -4
150 9
0   -1

##</code><code>##

my @a = ((0) x 361);

my @b = ((0) x 361);

my @matrix = (@a,@b)

while ($line = <IN>)
{
@record   = split(/\s+/, $line);
$a = $record[0]; 
$b  = $record[1]; 
@matrix [$a+180][$b+180] ++;
}