# untested!

use Encode qw(decode);
use Unicode::Semantics qw(up);

up($line = decode 'UTF-8', $line);

my $word = qr/\b(?!(?:AND|OR|XOR|NOT)\b)\w+/i;
$line =~ s/($word)\s*($word)/$1 AND $2/g for 1..2;