This method is fast, as the following benchmark shows:

Yeah, but it's also wrong, as the following code shows:

#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw( cmpthese );

my $count = shift || 100000;
my @test_array = (0 .. 99);
my (@array1, @array2);

sub map_bench
{
    @array1 = map { '?' } @test_array;
}

sub x_bench
{
    @array2 = '?' x @test_array;
}

map_bench;
x_bench;

print "\@test_array has ", scalar @test_array, " elements\n";
print "\@array1 has ", scalar @array1, " elements\n";
print "\@array2 has ", scalar @array2, " elements\n";

__END__
@test_array has 100 elements
@array1 has 100 elements
@array2 has 1 elements
[download]

The x operator will only return a multi-element list if all of the following conditions are met:

• The operator is in list context.
• The right-hand side of the operator is greater than 1.
• The left-hand side of the operator is surrounded by parens.

And the last condition isn't met. Here's a better benchmark, x is still winning, but not with such a margin:

#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw /cmpthese/;

our @test_array = (0 .. 99);
our (@array1, @array2);

cmpthese -2 => {
    map => '@::array1 = map {"?"} @::test_array',
    x   => '@::array2 = ("?") x @::test_array'
};

die "Benchmark failed" unless @test_array == @array1 &&
                              @test_array == @array2;

__END__

Benchmark: running map, x for at least 2 CPU seconds...
       map:  3 wallclock secs ( 2.09 usr +  0.03 sys =  2.12 CPU) @ 46
+08.49/s (n=9770)
         x:  2 wallclock secs ( 2.28 usr +  0.00 sys =  2.28 CPU) @ 14
+508.33/s (n=33079)
       Rate  map    x
map  4608/s   -- -68%
x   14508/s 215%   --
[download]

Abigail

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