It looks like intersection takes as its argument an AoH (array of references to hashes):

intersection( \%array1, \%wisconsin, \%rockford )
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What you have is an AoA, so you need to convert your AoH to an AoH -- or just make one in the first place. Here's one way, assuming that the "value" for each entry in the hash doesn't matter (here set to 1):

push @comp, { map { $_ => 1 } @array1 };
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That said, your code winds up a bit wooley, creating arrays, then hashes and so on, just to get an intersection hash from which you have to extract the keys to get your intersection list.

Instead, you might want to use a nice module like List::Compare that lets you just work with an AoA and gives you back an array:

use strict;
use List::Compare;

my @array1 = qw{ bob larry melon fruit};
my @array2 = qw{ bob larry melon apple};
my array3 = qw{ bob larry fruit apple};

my @comp;

push @comp, [@array1];
push @comp, [@array2];
push @comp, [@array3];

my $lc = List::Compare->new( @comp );

my @intersection = $lc->get_intersection;
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