I prefer to use references all the way down, it reads better to me this way.

my $array_ref = [
  { foo=> 1, herp => 'a'},
  { bar => 2, derp => 'b'},
  { baz => 3, burp => 'c'},
];

# to iterate
foreach my $h (@$array_ref) {
  foreach $k (keys %$h) {
    ++$h->{$k}; # note ++ "increments" strings as well
  }
}
[download]

Or in a more direct way.

my $array_ref = [
  { foo=> 1, herp => 'a'},
  { bar => 2, derp => 'b'},
  { baz => 3, burp => 'c'},
];

# unrolled iteration loop
++$array_ref->[0]->{foo}; # now 2
++$array_ref->[0]->{herp}; # now b
++$array_ref->[1]->{bar}; # now 3
++$array_ref->[1]->{derp}; # now c
++$array_ref->[2]->{baz}; # now 4
++$array_ref->[2]->{burp}; # now d
[download]