Yes, it should be possible but the syntax might get sticky. As scorpio17 says in this thread, what you want to do with the data is one the the deciding factors in how you want to store it. (Along with other factors). If the data is too large to load into memory, you may need to consider some of the suggestions offered by others here.

If the requirement is just to produce output like you provided, a Hash of Hashes may be a good choice. 

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

my %data;

while (<DATA>) {
    my ($user, $site, $cat) = /"([^"]+)"/g;
    $data{$user}{$site} = $cat;
}

for my $user (keys %data) {
    my $href = $data{$user};
    print $user, "\n";
    print "\tWebsite: $_, Category: $href->{$_}\n" for keys %$href;
}

__DATA__
user="john" website="www.yahoo.com" type="Entertainment"
user="david" website="www.facebook.com" type="Social Networking"
user="john" website="www.facebook.com" type="Social Networking"
user="mike" website="www.google.com" type="Search Engines"

[download]
Output was: 
john
        Website: www.yahoo.com, Category: Entertainment
        Website: www.facebook.com, Category: Social Networking
mike
        Website: www.google.com, Category: Search Engines
david
        Website: www.facebook.com, Category: Social Networking

[download]
 Update: With a file this large, would it be likely for one user to visit the same website more than once?

In reply to Re^5: Hash of Hashes from file by Cristoforo
in thread Hash of Hashes from file by cipher

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