The way to dereference a subroutine reference is to use either & slightly differently than you have, or better, to use parentheses so that you can pass arguments to the subroutine. For clarity, I'll switch your outer loop to a while with an each.

while (my ($key, $subs) = each %HoL) {
    foreach my $sub (@$subs) {
        $sub->();
        # or &$sub;
    }
}
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To go back to your example, one problem is that you're looping over the whole hash, where normally you'd want to use keys or values. This works:

for my $key (keys %HoL) {
  for my $i (@{$HoL{$key}}) {
    $sub->();    
    # or &$i;
  }
}
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