Just thought I'd muddy the waters a bit more, for fun: 

cmpthese -2, {
    for_0   => sub { for_loop( \@match_0 ) },
    for_25  => sub { for_loop( \@match_25 ) },
    for_50  => sub { for_loop( \@match_50 ) },
    for_75  => sub { for_loop( \@match_75 ) },
    for_100 => sub { for_loop( \@match_100 ) },

    grep_0   => sub { grep_loop( \@match_0 ) },
    grep_25  => sub { grep_loop( \@match_25 ) },
    grep_50  => sub { grep_loop( \@match_50 ) },
    grep_75  => sub { grep_loop( \@match_75 ) },
    grep_100 => sub { grep_loop( \@match_100 ) },
    
    fastgrep_0   => sub { fastgrep_loop( \@match_0 ) },
    fastgrep_25  => sub { fastgrep_loop( \@match_25 ) },
    fastgrep_50  => sub { fastgrep_loop( \@match_50 ) },
    fastgrep_75  => sub { fastgrep_loop( \@match_75 ) },
    fastgrep_100 => sub { fastgrep_loop( \@match_100 ) },
    
    noretfor_0   => sub { noretfor_loop( \@match_0 ) },
    noretfor_25   => sub { noretfor_loop( \@match_25 ) },
    noretfor_50   => sub { noretfor_loop( \@match_50 ) },
    noretfor_75   => sub { noretfor_loop( \@match_75 ) },
    noretfor_100   => sub { noretfor_loop( \@match_100 ) },
    
    noretgrep_0   => sub { noretgrep_loop( \@match_0 ) },
    noretgrep_25   => sub { noretgrep_loop( \@match_25 ) },
    noretgrep_50   => sub { noretgrep_loop( \@match_50 ) },
    noretgrep_75   => sub { noretgrep_loop( \@match_75 ) },
    noretgrep_100   => sub { noretgrep_loop( \@match_100 ) },
};

sub for_loop {
    my @matches;
    for ( @{$_[0]} ) {
        push @matches, $_ if /x/;
    }
    return @matches;
}

sub grep_loop {
    my @matches = grep /x/, @{$_[0]};
    return @matches;
}

sub fastgrep_loop {
    return grep /x/, @{$_[0]};
}

sub noretfor_loop {
    for (@{$_[0]}) {
        $_ =~ /x/
    }
}

sub noretgrep_loop {
    grep /x/, @{$_[0]};
}
__END__
(cropped to fit)
               Rate grep_100 grep_75 for_100 grep_50 for_75 for_50 gre
+p_25 for_25 noretfor_75
grep_100      134/s       --    -17%    -29%    -41%   -42%   -55%    
+-62%   -68%        -79%
grep_75       161/s      20%      --    -15%    -29%   -30%   -47%    
+-55%   -61%        -75%
for_100       189/s      41%     17%      --    -16%   -18%   -37%    
+-47%   -55%        -71%
grep_50       226/s      68%     40%     20%      --    -2%   -25%    
+-36%   -46%        -65%
for_75        231/s      72%     43%     22%      2%     --   -24%    
+-35%   -45%        -64%
for_50        302/s     125%     87%     60%     33%    31%     --    
+-15%   -28%        -54%
grep_25       356/s     165%    121%     88%     57%    54%    18%    
+  --   -15%        -45%
for_25        419/s     212%    160%    121%     85%    82%    39%    
+ 18%     --        -36%
noretfor_75   650/s     383%    303%    243%    187%   182%   115%    
+ 82%    55%          --
noretfor_100  680/s     406%    321%    259%    200%   195%   125%    
+ 91%    62%          5%
noretfor_50   693/s     416%    330%    266%    206%   200%   130%    
+ 95%    66%          7%
for_0         693/s     416%    330%    266%    206%   200%   130%    
+ 95%    66%          7%
noretfor_0    697/s     419%    332%    269%    208%   202%   131%    
+ 96%    66%          7%
noretgrep_50  700/s     421%    334%    270%    209%   204%   132%    
+ 96%    67%          8%
noretfor_25   701/s     421%    334%    271%    210%   204%   132%    
+ 97%    67%          8%
noretgrep_75  736/s     448%    356%    289%    225%   219%   144%    
+106%    76%         13%
fastgrep_0    740/s     451%    359%    291%    227%   221%   145%    
+108%    77%         14%
fastgrep_75   747/s     456%    363%    295%    230%   224%   147%    
+110%    78%         15%
fastgrep_100  752/s     460%    366%    298%    232%   226%   149%    
+111%    80%         16%
noretgrep_25  769/s     472%    376%    306%    240%   233%   154%    
+116%    84%         18%
noretgrep_0   769/s     472%    377%    307%    240%   233%   155%    
+116%    84%         18%
fastgrep_50   777/s     478%    381%    311%    243%   237%   157%    
+118%    85%         20%
noretgrep_100 781/s     481%    384%    313%    245%   238%   159%    
+119%    86%         20%
grep_0        796/s     492%    393%    321%    252%   245%   164%    
+123%    90%         23%
fastgrep_25   801/s     496%    396%    323%    254%   247%   165%    
+125%    91%         23%

[download]
I skipped "my @values = @{shift()};" in all of them, since this array copy seemed to be a big part of the run time. The point I would take from this is that the performance really depends more on the situation you use them in and how you use them. As kyle says, it's probably best to just use the one that is clearest. For me, that would be fastgrep_loop.
-driver8

In reply to Re^2: Battle Royal Grep vs For by driver8
in thread Battle Royal Grep vs For by Herkum

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