Change 

my %new2 =
hmap { $_[1]{nick} =~ /rbush|fred/ ?
      ($_[0], hmap { $_[0], $_[1] } %{$_[1]}) : () } %$h;

[download]

to 

my %new2 =
hmap { $_[1]{nick} =~ /rbush|fred/
          ? $_[0] => { hmap { $_[0], $_[1] } %{$_[1]} }
          : ()
     } %$h;

[download]

The relevant change is the curlies around the inner call to hmap. %{$_[1]} creates a list of the hash's content from the hash reference. You have to mirror that on the output side by creating a hash reference from the list.

You can't have it both ways. hmap can either return a list that can be used to initialize a hash or a hash reference.

An alternative would be to just pass hash references instead of the contents of hashes. 

sub hmap (&$)
{
    my $code = shift;
    my @i = %{ shift() };
    my @rv;
    push @rv, $code->(shift @i,shift @i) while @i;
    return { @rv };
}

my $new2 =
hmap { $_[1]{nick} =~ /rbush|fred/
          ? $_[0] => hmap { $_[0], $_[1] } $_[1]
          : ()
     } $h;

[download]

(Removed the useless local @_ and @_=. What do you think calling a sub does...)

Since we have an actual hash to work with instead of a list of its content, we can use each instead of flattening the hash into @i.

In reply to Re: hmap revisited by ikegami
in thread hmap revisited by zerohero

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