@new = map lc, @old;
@new = map ord, @old;
@new = map { sprintf('%02X', $_) } @old;

##</code><code>##

use List::MoreUtils qw( apply );
@new = apply { chomp; } @old;
@new = apply { tr/a-z/n-za-m/; } @old;

##</code><code>##

sub func {
   for (my $s = @_ ? $_[0] : $_) {
      ... do something with $_ ...
      return $_;
   }
}

$new = func($old);
@new = map func, @old;