#!/usr/bin/perl

# simple example, how perl can work with the output of a space delimited array
# and work with it as a matrix. An entry of the matrix can then be accessed
# for example m(3,3). Its easy then to make spreadsheet calculations within 
# perl, without having to use excel-type-tools. In this example, the 3'th row 
# is added up. 

#  usage examples: 
#  matrix.pl < file.in > file.out

@command=<STDIN>;
$delimiter=" ";
$num_of_rows=$#command+1;

$sum=0; 
for ($k=1; $k<=$num_of_rows; $k++) {
  $sum+= &m($k,3); 
} 
print $sum,"\n";

sub m {
   my @indices=@_;
   my $i=@indices[0]-1;
   my $j=@indices[1]-1;
   $line=@command[$i];
   @entries=split($delimiter,$line);
   $num_of_columns=$#entries;
   $entry=@entries[$j];
   return $entry;
}