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

my $datafile = "stuff.csv";
my @fields;
my $data;

open DATA, "<$datafile" or die "Could not open $datafile:$!\n";
# Grab the first (header) line, discarding the first two fields
$_ = <DATA> or die "Empty file";
chomp((undef, undef, @fields) = (split /\t/));

# Grab the rest, and populate the hashref
while (<DATA>) {
    chomp();
    my ($user, @userdata) = (split /\t/);
    $data->{$user}{$_} = shift @userdata for (@fields);
}
close DATA;