Hmm seems like HOP doesn't show how to reimplement plain map.

But as a side note, perlsub has an example for grep :

      And here’s a reimplementation of the Perl "grep" operator:

           sub mygrep (&@) {
               my $code = shift;
               my @result;
               foreach $_ (@_) {
                   push(@result, $_) if &$code;
               }
               @result;
           }
[download]

HTH!