Thanks everyone for the help. I tried the benchmark Abigail-II did on my machine, with a map thrown in for good measure, and got slightly different results -- strangely, the simple push won! 
#!/usr/bin/perl
 
use strict;
use warnings;

use Benchmark qw /cmpthese timethese/;
    
our $size = 100_000;
    
cmpthese timethese (-10 =>  {
    push      =>  'my @arr; push @arr => $_ for 0 .. $::size - 1',
    map       =>  'my @arr; @arr = map {$_} (0 ..  $::size - 1)',
    assign    =>  'my @arr; $arr [$_] =  $_ for 0 .. $::size - 1',
    assignpre =>  'my @arr; $#arr = $::size - 1;
                            $arr [$_] =  $_ for 0 .. $::size - 1', 
    slice     =>  'my @arr; @arr [0 .. $::size - 1] = (0 .. $::size - 
+1)',
    slicepre  =>  'my @arr; $#arr = $::size - 1;
                            @arr [0 .. $::size - 1] = (0 .. $::size - 
+1)',
} => 'none');
__END__

            Rate       map  slicepre     slice assignpre    assign    
+  push
map       7.68/s        --      -34%      -36%      -45%      -47%    
+  -48%
slicepre  11.7/s       52%        --       -3%      -17%      -19%    
+  -21%
slice     12.1/s       57%        3%        --      -14%      -17%    
+  -18%
assignpre 14.1/s       83%       20%       16%        --       -3%    
+   -5%
assign    14.5/s       89%       24%       20%        3%        --    
+   -2%
push      14.7/s       92%       26%       22%        5%        2%    
+    --

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Here is what I was running: 
This is perl, v5.6.1 built for i386-linux
Linux cchan.acsys.com 2.4.8-26mdk #1 Sun Sep 23 17:06:39 CEST 2001 i68
+6 unknown

[download]

In reply to Re: Re: array pre-allocation trick by Anonymous Monk
in thread array pre-allocation trick by Anonymous Monk

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