use strict;
use warnings;

my ($filename, @mainword, $distance, @search) = @ARGV;

my $content;
open my $fh, '<', $filename or die $!;
local $/ = undef;
$content = <$fh>;
close $fh;

my @docs = split 'Document ', $content;
foreach my $doc ( @docs ) {

    my $count = 0;

    my $mainword = '(' . (join '|', map { "\Q$_\E" } @mainword) . ')';
    my $search = '(' . (join '|', map { "\Q$_\E" } @search) . ')';


    for (my $dist = 0; $dist <= $distance; $dist++) {
        while ( $doc =~ /
            (?:^|\W)                        
            $search                        
            (?=                           
                (?:\W++\w++){$dist}       
                \W++\Q$mainword\E         
            )
            /ixsg
        )
        {
            print " found [$1] at ", $-[1], "\n";

            $count++;
        }

        while ( $doc =~ /
            (?:^|\W)
            \Q$mainword\E
            (?=
                (?:\W++\w++){$dist}
                \W++$search
            )
            /ixsg
        )
        {
            print "-found [$1] at ", $-[1], "\n";
            $count++;
        }
    }

    print "match: $count\n";
}