use strict;  
use warnings;  
use Data::Dumper;  
 
my ($filename, $mainword_str, $distance, $search_str) = @ARGV;  
 
my @mainword = split /\s*,\s*/, $mainword_str;  
my @search = split /\s*,\s*/, $search_str;  
 
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";  
}

my @mainword = split /\s*,\s*/, $mainword_str;   
my @search = split /\s*,\s*/, $search_str;  
 
my $mainword = '(' . (join '|', map { "\Q$_\E" } @mainword) . ')';   
my $search = '(' . (join '|', map { "\Q$_\E" } @search) . ')';

$mainword_str =~ s/\s*,\s*/|/; 
$search_str   =~ s/\s*,\s*/|/; 
 
my $mainword = qr!($mainword_str)i!; 
my $search   = qr!($search_str)i!;