my $string = '+book +dog +cat';

##</code><code>##

"+book", "+dog", "+cat"

##</code><code>##

my $string = '+book +dog +cat';
my @raw_params = split /\s+/, $string;
my @quoted_params = map { qq{"$_"} } @raw_params;
my $quoted_params_string = join ", ", @quoted_params;
print $quoted_params_string;