Hmmm ,

I think using strictures (use warnings; use strict;) would have undoubtedly helped you here, since between them they'd have pointed out that $rules is undefined in the regular expression i.e. in your snippet

if($line=~/^Request:($rules)/i){
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should, I think, read

if($line=~/^Request:($rule)/i){
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Also note that

foreach (@rules ) {
    $rule = $_;
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is better written as ...

foreach my $rule (@rules)
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Moreover, given that the action is the same for every matched rule, I'd modify your snippet to read

use warnings;
use strict;
use autodie;
use File::Tail;

local $|++;

open FH, "<rules.txt";
my $rules_re = join '|', <FH>;
close FH;

$name="C:\\users\\Mizo\\desktop\\log.txt;
$file=File::Tail->new(name=>$name, maxinterval=>1,interval=>1, adjusta
+fter=>1);

while (defined($line=$file->read())) {
    print $line if ($line=~/^Request:($rules_re)/i);
}
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Update:

Added suggested modifications ,p>