You Have it here

use strict;
use warnings;

my $contents;
my $hi_from;
my $hi_to;
my $bye_from;
my $bye_to;

open (FH,"filename") or die ("Can't open");
while(<FH>)
{
    chomp($_);
    $contents.=$_;
}
($hi_from=$contents)=~s/hi:\s+(\d*)/$1/;
$hi_from=$1;

($hi_to=$contents)=~s/(hi:\s+)(?!.*hi:)(.*\d+)(?=.*bye:)/$2/;
($hi_to=$2)=~s/\d+//;
$hi_to=~s/.*\s(\d+)/$1/;

($bye_from=$contents)=~s/bye:\s+(\d*)/$1/;
$bye_from=$1;
    
    
($bye_to=$contents)=~s/(bye:\s+)(?!.*bye:)(.*\d+)/$2/;
($bye_to=$2)=~s/\d+//;
$bye_to=~s/.*\s(\d+)/$1/;

print "\n\n\nHi From: $hi_from\n";
print "Hi to: $hi_to\n";
print "Bye from: $bye_from\n";
print "bye to: $bye_to\n";
[download]

First I am reading from the file and creating a flat-string of the file contents.Then I go about doing a lot of regexe's to ensure we get what we want!!
Sorry if you find the regexe's difficult.It will help you learn a lot of things about regexe's, if you can decipher it!!