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 = @_;
    local @_;
    my @rv;
    push @rv, $code->(@_=(shift @i,shift @i)) while @i;
    @rv;
}
                                    
my %new =
hmap { $_[1]{nick} =~ /rbush|fred/ ? ($_[0], $_[1]) : () } %$h;
                       
my %new2 =
hmap { $_[1]{nick} =~ /rbush|fred/ ?
      ($_[0], hmap { $_[0], $_[1] } %{$_[1]}) : () } %$h;

print "new = " . Dumper (\%new) . "\n";
print "new2 = " . Dumper (\%new2) . "\n";