Just for curiosity, I tried Algorithm::Loops as well. The results seem to indicate that if you want to go for readability you'd better use it, if you really need speed it's better to roll your own. Bewaring of the pitfalls.

#!/usr/bin/perl -w
use strict;
my @elem = (0..100_000);

use Benchmark ':all';
use Algorithm::Loops 'Filter';
cmpthese ( 100, {
   'mapn' => sub { my @e = @elem; @e = map { $_ if (s/0/./g || 1) } @e
+ },
   'for ' => sub { my @e = @elem; for (@e) { s/0/./g } },
   'mapc' => sub { my @e = map { $_ if (s/0/./g || 1) } @elem },
   'Filter' => sub { my @e = Filter { s/^\s+// } @elem },
});

__END__

~/sviluppo/perl> ./loops.pl
         Rate Filter   mapn   mapc   for
Filter 4.00/s     --    -1%   -39%   -53%
mapn   4.06/s     1%     --   -38%   -52%
mapc   6.57/s    64%    62%     --   -23%
for    8.54/s   113%   110%    30%     --
[download]

Indeed, the implementation of Filter resembles that of for, but its generality has two drawbacks:

• There are two copies, one entering the function and one upon exit
• the provided subroutine reference gets called, wich IMHO should trigger some penalty.

Just my 2c.