Have you tried it? It copies -and- modifies -both-.

my @elem = ( 1..20 );
my @e = map { $_ if (s/0/./g || 1) } @elem;
print join( " ", @elem ), "\n";
__END__
1 2 3 4 5 6 7 8 9 1. 11 12 13 14 15 16 17 18 19 2.
[download]

I understand -why- you put the logical path there. Just saying s/0/./g; $_; makes more sense than the if and or.

But you are quite right. It is moot. map is still slower, though arguably clearer in the $_ + 2 case. I don't know that map {} is ever an optimization.

I would use grep to filter records, or map to preprocess going into a sort. I find that makes sense to me coding-wise. I doubt that it is better speed-wise.

addendum:

Okay, here is a case where I think map is cleaner and (slightly) faster:

my @elem = map { int rand 1000 } 1..10000;

sub map_s {
   my @mod_sorted = sort { $a <=> $b } map { $_ % 2**6 } @elem;
}

sub for_s {
   my @a;
   for ( @elem )
   {
      push @a, $_ % 2**6;
   }
   my @mod_sorted = sort { $a <=> $b } @a;
}
__END__
      Rate for map
for 15.8/s  -- -4%
map 16.5/s  4%  --
[download]