my $log = "";
for my $item (@stuff) {
  do_something($item);
  $log .= "Email sent to: $item<br>\n";
}

print $log_file $log;
[download]

If I understand you correctly, here's an untested example that should provide guidance:

my $count = 0;
my @sent;

while (get_entry_from_db()){
    if (/match/){
        ...; # send email and do other stuff
        $count++;
        push @sent, [$contact, $email];
    }
}

print "users mailed: $count\n";

for my $entry (@sent){
    my ($contact, $email) = @$entry;
    print "email sent to: $contact <$email><br>";
}
[download]

I've used an array of arrays here, instead of just appending the full string to the array, but you can go that route as well.

update: changed default var to named in for() loop for clarity

So I would use another loop within my loop? Here's what I'm doing:

$SQL = "Select * from database where (TO_DAYS(enddate) - TO_DAYS(Now()
+) = 8) AND payment!='premium'";
&Do_SQL;
$recordcount = $sth->rows;
if ($recordcount > 0) { 
    $sendEmails = 'yes';
    }
    
if ($sendEmails eq 'yes') {
    $count = 0;
    while ($pointer = $sth->fetchrow_hashref) {
        $contact = $pointer->{'contact'};
        $toemail = $pointer->{'email'};


    open (MAILPROG.....";
    SEND THE EMAIL HERE....
    close (MAIL);
    
    print "email sent to: $contact <$toemail>\n";
    $count++
}
    print "Sent $count emails.\n";
    
    $action = "Email Reminders sent!";
    $log = "Sent $count emails.";
    &log_it;
[download]

I'd like $log to also have every email address that received an email. It would look something like this in the log:

Sent 4 emails.<br>
Email sent to user1<br>
Email sent to user2<br>
Email sent to user3<br>
Email sent to user4<br>
[download]

I need to get the $log variable within my existing loop but have it updated with every email. So do I have to run a separate loop within my loop?

#!/usr/bin/perl
use DBI;
my $dbfile = 'test.db';      # your database file

my $need2create = ! -f $dbfile;
my $dbh = DBI->connect(          # connect to your database, create if
+ needed
    "dbi:SQLite:dbname=$dbfile", # DSN: dbi, driver, database file
    "sq",                          # no user
    "lite",                          # no password
    { RaiseError => 1 },         # complain if something goes wrong
) or die $DBI::errstr;

my $table = 'test';
my @rows  = qw(id hobby email);

if($need2create){
    print "Creating $dbfile -> $table \n";
    $dbh->do("create table $table (".join(',',@rows).')')  or die $DBI
+::errstr;
    my @DATA = ('1|chess|camelot@aorta.com','2|math|dude@oops.no','3|m
+ath|foo@bar.com');
    for my $data (@DATA){
        $str ="insert into '$table' ('".join("','",@rows)."')"." value
+s ('".join("','",split(/\|/,$data))."')";
        print $str ."\n";
        $dbh->do($str)  or die $DBI::errstr;
    }
 }
 

$sql ="select * from $table";
my $sth = $dbh->prepare($sql);
$sth->execute(); 
my @SENDTO;
while (my @row = $sth->fetchrow_array) { # retrieve one row
    if($row[1]=~/math/i){
        print "emailing $row[2]\n";
        push(@SENDTO, $row[2]);
        # print "". join(", ", @row), "\n";
    }
}

for my $who (@SENDTO){
    $log = "I have emailed $who\n";
    print $log;
    &log_it;
}
[download]

Prints:

emailing dude@oops.no
emailing foo@bar.com
I have emailed dude@oops.no
I have emailed foo@bar.com
[download]

Alternative is that you concatenate your string with newlines, thus:

my $SENDTO = ""; # start with empty string
while (my @row = $sth->fetchrow_array) { # retrieve one row
    if($row[1]=~/math/i){
        $SENDTO .= "emailing $row[2]\n";
        push(@SENDTO, $row[2]);
    }
}

$log = $SENDTO;
&log_it;
[download]