Why is this getting so much up votes. People still advertising how to slice hashes using map and grep when the Perl language has more elegant ways to slice hashes.

use strict ;
use warnings ;
use Data::Dumper ;

my $source = {
    f1 => 'garbage',
    f2 => 'more garbage',
    f3 => 'important data',
    f4 => {
        this => 'sub hash',
        is   => 'garbage'
    },
    f5 => {
        f6 => 'more important data',
        f7 => {
            more => 'garbage',
            f8   => 'important data',
        },
        f9 => 'garbage',
    },
    f10 => [ 'important', 'data' ],
    f11 => [ 'more', 'garbage' ]
};

my $filter = {
    f3 => 1,
    f5 => {
        f6 => 1,
        f7 => {
            f8 => 1
        }
    },
    f10 => 1
};

sub sliceTheWholeDarnThing {
    my $s = $_[0] ;
    my $f = $_[1] ;
    my $n = {} ;
    my @keysToGet = keys %{ $f } ;
    @{ $n }{ @keysToGet } = @{ $s }{ @keysToGet } ;
    foreach ( keys %{ $n } ) {
        if ( ref $n->{ $_ } eq 'HASH' ) { 
            $n->{ $_ } = sliceTheWholeDarnThing( $s->{ $_ }, $f->{ $_ 
+} ) ;
        }
    }
    return $n ;
}

my $newHash = sliceTheWholeDarnThing( $source, $filter ) ;

print Dumper( $newHash ) ;
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