Yes, declaring  my %h2; fixed that problem. Now it seems that I can't run it because of perl v 5.8.8 XD

Note that since Perl 5.9.0 a // can also be the defined-or
    construct, not just the empty search pattern.  Therefore code writ
+ten
    in Perl 5.9.0 or later that uses the // as the defined-or can be
    misparsed by pre-5.9.0 Perls as a non-terminated search pattern.
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Looks like your questions have been well answered.

I just want to note that it is good that you use strict and warnings. It is even better than you now understand some of what they do. You'll probably recognise these problems immediately next time you encounter them and not have to ask.

But don't stop there. Read the documentation on both pragmas, and play with a few small test scripts trying their variations. Whilst the blanket application of both is generally okay, there are times when it is good to understand their details and be selective in which of their facilities you apply.

Don't be tempted by the false "labour saving" of modules replace that those two short lines with one long one.

You might also look into the differences between warnings and -w on the shebang line. For instance, you might conclude that the extra bells and whistles of the former are largely redundant most of the time, if you, like most people, strive to write your code so that it avoids the situations that raise the warnings; rather than opt to silence them by force.

And realise that on those occasions when you do choose to silence a warning, no warnings works just fine in conjunction with -w

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

RIP an inspiration; A true Folk's Guy

C style Logical Defined Or

is exactly equivalent to defined($a) ? $a : $b

As well, assuming all values are guaranteed to be non-zero numbers, you can swap that to a ||.