#!/usr/bin/perl
use warnings;
use strict;

   main();

   sub main{
      # open file
      my $file = shift @ARGV;
      open FILE1, '<', $file or die "Can't open '$file': $!";

      my %caseCount;
      # Use a while loop to read through the data
      while ( <FILE1> ) {
         my $caseNumber = ( split /\t/ )[ 1 ];
         $caseCount{ $caseNumber }++;
      }
      # close the file you don't need it any more
      close FILE1;

      #do something here with values in %caseCount
      #  DoSomething is an example of how to call a function
      DoSomething(\%caseCount);
   }

   sub DoSomething{
      my $hashref = shift;
      foreach my $key (sort keys %{$hashref}){
         print "$key - ${$hashref}{$key}\n";
      }
   }