Hello adriang,

I realise your code snippet is just for illustration; still, it may be instructive to note its various problems:

1. while ( my $key=keys(%hash) {

   Compile error: the second closing parenthesis is missing.

2. my $key=keys(%hash)

   Logic error: in scalar context the keys function returns the number of keys in the hash, not the keys themselves. You need a for loop here:

   for my $key (keys %hash) {
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3. keys %hash

   Logic error: since you want to exit the loop when a certain key is reached, the behaviour of the code depends on the order in which the keys are returned; but this order is “apparently random” (keys). To get deterministic behaviour, you need to sort the keys. For example:

   for my $key (sort keys %hash) {
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4. }  $hash{$key}=$verb;

   Compile error: if you’re running under use strict; (and you should be!), you will see this error message:

   Global symbol "$key" requires explicit package name at ...
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   You could fix this¹ by declaring my $key; before the loop, but it’s better style to restrict the scope of this lexical variable:

   for my $key (sort keys %hash) {
       if ($key eq $verb) {
           $hash{$key} = $verb;
           last;
       }
   }
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Update (Aug 23):
¹That is, you could fix the error message. But the code still wouldn’t work correctly, because $key is a temporary alias within the foreach loop (see “alias” in perlglossary), and it reverts to its pre-loop value when the loop ends.

Hope that helps,

Thanks for the quick answer. nr.1 - copy-paste error. nr.2 - 100% RIGHT. nr.3 - understand. nr.4 - fast writing error :-) Sorry, code nr.4 is not good for "since you want to exit the loop when a certain key is reached" because I want to create a hash element if the has key is not there. For now I use the "defined" function (below) to do the work but I realy want to know if there is other solution.

unless ( defined $email{"email"} ) {
    $email{$html->param("email")}=$html->param("name");
}
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exists should help you with this problem. As you may have noticed, looping over keys of a hash is much slower than accessing it by key. By the way, very often it is plain wrong.

print "before\n";
while( 1 ){ print for 1 .. 10; last }
print "after\n";
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Are you perhaps thinking of the continue statement? The $hash{$key}=$verb; line is unrelated to the while loop.

continue with wile is not good because "it is always executed just before the conditional is about to be evaluated again" I need a something that will be executed only once before the while loope exit and ofcourse if I use "last" in the loop that statment will never be executed. adrian