Nobody seems to have mentioned this, but you should be using exists to check for the existance of a hash key. In your example code, every key that has been brought into existance has been initialized with a value of 1. So one obvious potential problem is that you're checking for value in a key that doesn't exist. Hense, you get the warning about an uninitialized value. Is this a surprise? This is exactly what the exists function is for. 

my % pages = ( 'index' => 1,
               'me'    => 1,
               'stuff' => 1,
               'links' => 1 );
my $page = shift;
exit 0 unless exists $pages{$page} and $pages{$page} == 1;

[download]

This will not generate the uninitialized value warning, because the right hand side equality test only gets evaluated if the left side of the logical short-circuit 'and' evaluates to truth first (if the hash key exists).

If you happen to be in a situation where the key might exist but without any initialized value, you could chain a defined in there... 

exit 0 unless exists $pages{$page} and
              defined $pages{$page} and
              $pages{$page} == 1;

[download]

Not terribly elegant, but it does take into consideration all the possibilities.


Dave

In reply to Re: Unintialised value? by davido
in thread Unintialised value? by eoin

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