Even slower than the s/// suggestion. 
#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw 'cmpthese';

our @dates = (qw [092205 092305 092605]) x 100;
our (@sub, @pck, @mth, @spf,);

cmpthese(-10, {
    sub => '@sub = @dates; for (@sub) {s{(\d{2})(\d{2})(\d{2})}{$1/$2/
+$3}}',
    pck => '@pck = @dates; for (@pck) {$_ = join "/", unpack "A2 A2 A2
+", $_}',
    mth => '@mth = @dates; for (@mth) {$_ = join "/", /../g}',
    spf => '@spf = @dates; for (@spf) {$_ = sprintf "%d%d/%d%d/%d%d", 
+split //}',
});


__END__
      Rate  spf  sub  mth  pck
spf  368/s   -- -33% -60% -69%
sub  548/s  49%   -- -40% -53%
mth  909/s 147%  66%   -- -22%
pck 1171/s 218% 114%  29%   --

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In reply to Re^2: modify the contents of an array by Anonymous Monk
in thread modify the contents of an array by s_gaurav1091

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