Here's the simpler problem solved by regex.

#!/usr/bin/perl

use strict;
use warnings;

# Three friends live here.
# Each likes a different fruit and has a different profession.
# John doesn't like pears.
# The programmer likes cherries.
# Patrick is a blacksmith.
# Edward isn't a fisherman.
# Who likes apples?

$_ = <<END;
John apples,cherries,pears blacksmith,fisherman,programmer
Patrick apples,cherries,pears blacksmith,fisherman,programmer
Edward apples,cherries,pears blacksmith,fisherman,programmer
END

my @answer =
  /^
  (\w+)\ \S*\b(\w+)\b\S*\ \S*\b(\w+)\b\S*\n     # first line
  (\w+)\ \S*\b(\w+)\b(??{$2 eq $5})\S*\         # second line
    \S*\b(\w+)\b(??{$3 eq $6})\S*\n
  (\w+)\                                        # third line
    \S*\b(\w+)\b(??{$5 eq $8 || $2 eq $8})\S*\ 
    \S*\b(\w+)\b(??{$6 eq $9 || $3 eq $9})\S*\n

  (??{ $2 eq 'pears' })                   # John doesn't like pears
  (??{ $6 ne 'blacksmith' })              # Patrick is a blacksmith
  (??{ !grep $_ eq 'cherriesprogrammer',  # The programmer likes cherr
+ies
    $2.$3, $4.$5, $8.$9 })
  (??{ $9 eq 'fisherman' })               # Edward isn't a fisherman
  /x or die "failed";

print "$1 $2 $3\n$4 $5 $6\n$7 $8 $9\n\n";

print "@answer[ map $_ - 1,
  grep $answer[$_] eq 'apples', 0 .. $#answer] likes apples.\n";
[download]

outputs:

John apples fisherman
Patrick pears blacksmith
Edward cherries programmer

John likes apples.
[download]