Hi DarrenSol
Wonderful answers has been given, but maybe this little example / question could also "say" something.
If I give the following:

teacher students professor students
school class teacher desk table
chalk borad class school teacher
[download]

And I ask that for these:
1. print out all the words, without repeating any, 2. print out all the repeated words only, 3. print out the number of times each words is seen and probably an illustration this with an histogram.
How would you do these.

Let me answer QnS 1. and 2., allow you to figure question 3 and try your hands on other solution WITHOUT USING HASH

use strict;
use warnings;

my %hash;

while(<DATA>){
chomp;
  $hash{$_}++ for split;  
}

print join $/ => sort keys %hash; 
print $/,$/, join $/ => grep {$_ if $hash{$_} > 1} sort keys %hash;
__DATA__
teacher students professor students
school class teacher desk table
chalk borad class school teacher
[download]

Solution:

1. borad
   chalk
   class
   desk
   professor
   school
   students
   table
   teacher
   [download]

2. class
   school
   students
   teacher
   [download]

That brings me to a statement I read in Programming Perl a while a go that 'Until you start thinking in terms of hashes, you aren’t really thinking in Perl.'

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