use strict;
use warnings;
my @labels = ('fee', 'fi', 'fo', 'fum');
open(my $fh, '<', "folks.txt") || die "can't open folks: $!";
my @list;
while (<$fh>) {
  chomp;
  push @list, [split /,/];
}

for my $element (@list) {
  print "$labels[0],$element->[0],$element->[1]\n";
}
for my $element (@list) {
  print "$labels[1],$element->[0],$element->[2]\n";
}
for my $element (@list) {
  print "$labels[2],$element->[0],$element->[3]\n";
}
for my $element (@list) {
  print "$labels[3],$element->[0],$element->[4]\n";
}

##</code><code>##

use strict;
use warnings;
my @labels = ('fee', 'fi', 'fo', 'fum');
open(my $fh, '<', "folks.txt") || die "can't open folks: $!";
my @list;
while (<$fh>) {
  chomp;
  push @list, [split /,/];
}

for my $i (0 .. 3) {
  for my $element (@list) {
    print "$labels[$i],$element->[0],$element->[$i+1]\n";
  }
}

##</code><code>##

use strict;
use warnings;
my @labels = ('fee', 'fi', 'fo', 'fum');
open(my $fh, '<', "folks.txt") || die "can't open folks: $!";
my @list;
while (<$fh>) {
  chomp;
  my @line = split /,/;
  my %hash = (number => shift @line);
  for my $i (0 .. $#labels) {
    $hash{$labels[$i]} = $line[$i];
  }
  push @list, \%hash;
}

for my $label (@labels) {
  for my $element (@list) {
    print "$label,$element->{number},$element->{$label}\n"
  }
}