use strict;
use warnings;
use strict;

my @inColors = (
    ['blue', 'foo'],
    ['red', 'bar'],
    ['blue', 'baz'],
    );
my %colors;

for my $inColor (@inColors) {
    if (exists $colors{$inColor->[0]}) {
        print "Replacing $inColor->[0], $colors{$inColor->[0]} with $inColor->[1]\n";
    } else {
        print "Adding $inColor->[0], $inColor->[1]\n";
    }

    $colors{$inColor->[0]} = $inColor->[1];
}

##</code><code>##

Adding blue, foo
Adding red, bar
Replacing blue, foo with baz