# query_parser.pl

use strict;
use warnings;

use Data::Dumper qw( );
use QueryParser  qw( );

sub display {
   my ($expr, $tree) = @_;
   local $Data::Dumper::Indent = 0;
   print(Data::Dumper->Dump([$tree], [$expr]), "\n");
}

{
   my $parser = QueryParser->new();

   foreach my $expr (
      '( keyword1 )',
      '( keyword1 ) AND ( keyword2 )',
      '( keyword1 ) AND ( keyword2 ) AND ( keyword3 )',
      '( keyword1 ) NOT ( keyword2 )',
      '( keyword1 ) NOT ( keyword2 ) NOT ( keyword3 )',
      '( keyword1 ) AND ( keyword2 ) NOT ( keyword3 )',
      '( keyword1 ) NOT ( keyword2 ) AND ( keyword3 )',
      '( keyword1 OR keyword2 )',
      '( keyword1 ) AND ( keyword2 OR keyword3 )',
      '( keyword1 ) NOT ( keyword2 OR keyword3 )',
   ) {
      my $tree = $parser->parse($expr);
      display($expr, $tree);
   }
}