in reply to Map: Thou Has't Confounded Me For The Last Time! (Referring To The Array You Are Assigning To In Map)

There was a detailed thread on this before. I don't have time to search for it right now, but it was determined that

%hash = map { getkey($_) => $_ } @array;

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is closer to

@anon_temp = ();
foreach (@array) {
   push(@anon_temp, getkey($_), $_);
}
%hash = @anon_temp;

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than to

%hash = ();
foreach (@array) {
   $hash{getkey($_)} = $_;
}

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and that the %hash = @anon_temp; accounts for the speed difference.

As for your other question, my $something = $value if $something is similar to (or the same as?) (my $something = $value) if $something. The my in executes only if $something was true before this statement. Never use if, unless, etc on a my.

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Re^2: Map: Thou Has't Confounded Me For The Last Time! (Referring To The Array You Are Assigning To In Map)
by halley (Prior) on Feb 14, 2005 at 14:46 UTC
    I feel that ikegami has provided the most accurate explanation of the map operator.

    This is the beginning of the road to understanding the difference between a list and an array, by the way. You'll see both terms in the perldocs, but you won't see a lot to explain the difference. An array is a variable type. A list is what an array contains, but lists often exist without any array at all. The @anon_temp in ikegami's example is one way of explaining such a list.

    Note that foreach is a statement type, while map is an operator. This operator takes one list, and transforms it into a completely new list, element by element.

    --
    [ e d @ h a l l e y . c c ]

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      For future reference, there is a good explanation in the perldocs. It's in perlfaq4, accessible directly via perldoc -q 'list and':

      Found in /usr/share/perl/5.8/pod/perlfaq4.pod
       What is the difference between a list and an array?

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Re^2: Map: Thou Has't Confounded Me For The Last Time! (Referring To The Array You Are Assigning To In Map)
by ikegami (Patriarch) on Feb 14, 2005 at 15:24 UTC
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