Your file is a strange format, so I created it programtically, if this is incorrect then please say so. I also simplified the code for these purposes, removing the email components:

#!/usr/bin/perl
use strict;
use warnings;

my $pattern ='hello';

open (my $fh, '>', 'results.txt') or die "results.txt: $!";
binmode $fh;
print $fh "\nhello";
close $fh;

open FILE, "< results.txt" or die "Can't open results output file: $!"
+;
while (my $line=<FILE>)
{  
    if($line=~m/\b$pattern/)
    {
        print " match: <$line>";
    }
}

close FILE;
[download]

This matched "hello" as expected, just once. I suggest that maybe your file is not in exactly the format you say.
You might like to display it using, for example od -xc results.txt if you are on UNIX/Linux.

By the way, you are taking a risk running code without warnings and strict set. For example, in the commented out sysopen the flags should be O_RDWR (assuming you use Fcntl;), not o_RDWR, which you won't pickup.