On Wed, Mar 4, 2009 at 7:07 PM, Shmuel Fomberg <[email protected]> wrote:
> Hi All.
>
> Today I've seen a weird behavior in a program. I had something like:
>
> our @list = qw{one two three};
>
> use constant VAR => {
> key => "value",
> map( { ( $_ => 16 ) } @list ),
> key2 => "value2",
> };
>
> To my surprise, VAR contained only key and key2.
> I theorized that it is because "use constant" is set in compile time,
> and @list is empty in that time. @list is populated in run-time, but
> that is too late for VAR.
>
> Am I right or is there other reason for this?
Yes, that is exactly what happened. If you use the "our" statement
within a BEGIN:
BEGIN {
our @list = qw{one two three};
}
you can make it work as you thought at first.
The BEGIN blocks and use statements (as you already said contrasting
compile-time and run-time) create a different order of execution
besides the textual one, which is quite surprising some times.
It is like you have written:
BEGIN {
our @list; # the declarations happen at compile time, so that the
references down below don't err on "strict" mode
require constant;
constant->import( VAR => {
key => "value",
map( { ( $_ => 16 ) } @list ),
key2 => "value2",
});
}
# then everything else not in a "BEGIN"
@list = qw{one two three};
> Tested on Perl 5.6.
It is not different in Perl 5.8 or 5.10.
Regards,
Adriano
> Shmuel.
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