c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @positive = qw(nation conceived liberty created equal foo);
 my @negative = qw(fourscore SEVEN fOrTh fathers continent bar);
 ;;
 my $sentence = 'FoUrScOrE and seven years ago '
              . 'our fathers brought forth, on this continent, '
              . 'a new nation, conceived in liberty, and dedicated '
              . 'to the proposition that all men are created equal. '
              . 'Repeat seven nation fathers nation.'
              ;
 ;;
 my %pos = map { lc($_) => 0 } @positive;
 my $rx_pos = make_regex(\%pos);
 print 'for debug: positive rx: ', $rx_pos;
 ;;
 my %neg = map { lc($_) => 0 } @negative;
 my $rx_neg = make_regex(\%neg);
 print 'for debug: negative rx: ', $rx_neg;
 ;;
 my %other;
 my $rx_undefined = qr{ (?! $rx_pos | $rx_neg) }xms;
 my $rx_word      = qr{ \b [[:alpha:]]+ \b }xms;
 ;;
 ++$pos  { lc $_ } for $sentence =~ m{ $rx_pos }xmsg;
 ++$neg  { lc $_ } for $sentence =~ m{ $rx_neg }xmsg;
 ++$other{ lc $_ } for $sentence =~ m{ $rx_undefined $rx_word }xmsg;
 ;;
 dd \%pos;
 dd \%neg;
 dd \%other;
 ;;
 ;;
 sub make_regex {
   my ($hr_wordlist) = @_;
   ;;
   my ($rx) =
     map  qr{ (?i) \b (?: $_) \b }xms,
     join '|',
     map  quotemeta,
     reverse sort
     keys %$hr_wordlist
     ;
   ;;
   return $rx;
   }
"
for debug: positive rx: (?msx-i: (?i) \b (?: nation|liberty|foo|equal|created|conceived) \b )
for debug: negative rx: (?msx-i: (?i) \b (?: seven|fourscore|forth|fathers|continent|bar) \b )
{ conceived => 1, created => 1, equal => 1, foo => 0, liberty => 1, nation => 3 }

{ bar => 0, continent => 1, fathers => 2, forth => 1, fourscore => 1, seven => 2 }

{
  a           => 1,
  ago         => 1,
  all         => 1,
  "and"       => 2,
  are         => 1,
  brought     => 1,
  dedicated   => 1,
  in          => 1,
  men         => 1,
  new         => 1,
  on          => 1,
  our         => 1,
  proposition => 1,
  repeat      => 1,
  that        => 1,
  the         => 1,
  this        => 1,
  to          => 1,
  years       => 1,
}