#!/usr/bin/perl -w
use strict;

my $file = 'd:/temp/file.csv';
my %hash;

open(FILE, $file) or die("Can't open $file: $!\n");
while (<FILE>) {
  my ($src, $duh) = split /,/, $_, 2;
  $hash{$src}++;
}
close(FILE);

foreach my $ip (sort({$hash{$a} <=> $hash{$b}} keys %hash)) {
  print "$ip was seen $hash{$ip} times\n";
}