use strict;
use warnings;

my $str1 = q{CHARLIE ROOT}; 
my $str2 = q{HARRY NODE}; 
my $output = process( $str1, $str2 ) 
    . q{ } 
    . process( $str2, $str1 ); 
print $output, qq{\n}; 

sub process { 
    my ( $word1, $word2 ) = @_; 
    my @letters_to_remove = grep{ ! m/\s+/; } 
                                split //, $word2; 
    my $remove_str = join q{}, 
                         q{[}, 
                         @letters_to_remove, 
                         q{]}; 
    my $result = $word1; 
    $result =~ s/$remove_str//g; 
    return $result; 
}

##</code><code>##

CLI T Y ND