sub hashCopyByKey {
     my ($to, $from, @key) = @_;
     @key = grep{ exists $from->{$_} } @key;
     @{$to->{@key}} = @{$from->{@key}};
}

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

my @sel_keys = qw/red green/;
my %hash_source = ( red => '#ff0000', green => '#00ff00', blue => '#0000ff', );

my %hash_target = hashAssignByKeys(\%hash_source, @sel_keys);
print Dumper \%hash_target;
exit;

sub hashAssignByKeys {
    my ($source, @keys) = @_;
    map { $_, $source->{$_} } grep { exists $source->{$_} } @keys;    
}