I copy and pasted the code sample from above, but it failed to compile. I tried a few things but couldn't get it to work (the error is in the dense part where I don't fully understand the syntactical rules). Offending line seems to be:

snippet:

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

Here's the compilation error:

bash-3.2$ perl hmap_good2.pl
syntax error at hmap_good2.pl line 39, near "] =>"
syntax error at hmap_good2.pl line 40, near ":"
Execution of hmap_good2.pl aborted due to compilation errors.
[download]

Possibly I'm missing something simple? Full script pasted below:

use Data::Dumper;

my $h =
{
    1 =>
    {
        nick => 'rbush',
        phone => '5551212',
        bday => '3/12/1965',
    },

    3 =>
    {
        nick => 'ernest',
        phone => '5553300',
        bday => '3/12/1971',
    },

    5 =>
    {
        nick => 'fred',
        phone => '1112300',
        bday => '5/01/1972',
    },

};

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;

print Dumper ($new2), "\n";
[download]

Note that the second version (the hash ref one) has the same compile error, but I could get that to work by surrounding the returned hash in "()", i.e.:

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