You might want to rephrase the problem into pseudo code, something like this:

#for each line {
#  split line into bits;
#  has string been seen {
#    do something;
#  }
#}
[download]

If you are still stuck then post back the pseudo-code and someone will probably help you fill it. However without the pseudo code it is difficult to know exactly what you want to achieve...

--tidiness is the memory loss of environmental mnemonics

This sounds like homework. Are you sure you don't want to give this a whirl? It's a fairly basic script which reads a line, splits it, and stores the result in some sort of data structure. Why don't you try it yourself and post your code if you get stuck. The monks here could whip up a real slick perlish way to do it, but would your teacher really believe you wrote it if you are just starting out in perl? Plus, if someone else does all the work, you stay a newbie.

"You learn by doing", as my chemistry teacher used to say.

$ perl -F, -lane 'push@{$h{$F[0]}},$F[3]}{$"=",";print"$_,@{[reverse@{
+$h{$_}}]}"for sort keys%h' < input.txt
Kim,on,off
Rada,one,zero
Tyra,on,off
[download]

I wouldn't turn that in if I were you though...

-sauoq
"My two cents aren't worth a dime.";

Another question: are the second and third fields of each record important or can they be thrown away?

Assuming they are unimportant, I suggest you use a hash of arrays (if you want to keep all fourth fields, even if they are repeated) or a hash of hashes (if you want to collapse repeated fourth fields into one item).

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law

I'm wondering if this is some kind of trick your teacher is playing on you to see if you spot that "zero" can't be numerically sorted or something?
--

“Every bit of code is either naturally related to the problem at hand, or else it's an accidental side effect of the fact that you happened to solve the problem using a digital computer.”
M-J D

This may be what you're looking for:

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

my %names;

while (<DATA>) {
    chomp;
    my ($name, $lastThingy) = (split /,/)[0,3];
    push @{$names{$name}}, $lastThingy;
}

foreach my $key (keys %names) {
    my $values = join ',', (@{$names{$key}});
    print "$key,$values\n";
}

__DATA__
Kim,0,0,off
Kim,1,1,on
Tyra,0,0,off
Tyra,1,1,on
Rada,0,0,zero
Rada,1,1,one
[download]

Update: v5.6.1 built for cygwin-multi doesn't print out the key, but v5.8.0 built for MSWin32-x86-multi-thread does. Weird.

Cē