There are many examples already in the monastery, but here's one way:

#! /perl/bin/perl 

use Data::Dumper;

use strict;

my @letters = ("red","red","red","blue","white","yellow","blue","navy"
+,"navy","green","white","cars");

my %count = ();

$count{$_}++ for @letters;

print Dumper( \%count );
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