Actually, no, it isn't necessary to include that if statement.

Incrementing an undef value is such a common annoyance that recent releases of perl special-case it. It seems to have been documented somewhere between version 5.004 and 5.8.8. Quoting directly from perlop, which is currently for version 5.10.0,

The auto-increment operator has a little extra builtin magic to it....

undef is always treated as numeric, and in particular is changed to 0 before incrementing (so that a post-increment of an undef value will return 0 rather than undef).

(Update:) Now that I think of it, the conversion to boolean in 

    if ($countries{$entries[1]}) ...

[download]
is also a special case: undef is being silently converted to false, even when using warnings and strict. If it weren't, you would have to say 
    if (defined ($countries{$entries[1]})) ...

[download]
which would also be fairly annoying.

In reply to Re^2: Need help on hashes. by quester
in thread Need help on hashes. by ElMagnifico

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