#!/usr/bin/perl -w
use strict;
use List::Util qw(reduce);

while (<DATA>)
{
   chomp;
   my (@array) = split';',$_;
   
   my $ColumnNumber = 
      reduce { $array[$a] >= $array[$b] ? $a : $b } 1..@array-1; 
      
   print $ColumnNumber, "\n";  
}

=prints
3
3
2
=cut

__DATA__
id001;10;10;30
id002;30;20;50
id003;30;80;10