By using references:

use strict;

my %one; my %two; my %three;

my $hashes = [\%one, \%two, \%three];

for (@$hashes) {
  for my $k (keys %$_) {
    #do something
  }
}
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UPDATE: storing them in an array reference is not necessary, i just wanted to show how to do so. :) But you do have to store the hashes as reference or else they will 'flatten' into the array that contains them.

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)