There are many fine templating engines out there, Template::Toolkit being the most featureful, and pleasant. There are also HTML::Template and Text::Template

Since you're not doing anything too fancy, Text::Template will most likely be enough.

you will have to split your strings into proper data structures before you pass them to the template engine, but that's not too hard.

As f00li5h pointed out, the best approach would be to use a templating module.

To pick up where he left off and provide an example of how you can use split to separate your input data, I submit the following code:

use strict;
use warnings;

my $_mergeFields = "##fname##;##lname##;##email##;##phone##;";

my $_list_to_send_to = "Richard;Smith;myemail\@testmail.com;8005551212
+;|Toby;Johnson;email2\@testmail.com;8885551212|Chanty;Perkins;another
+\@test.com;8665551212;";

my $_message = qq~
Hello ##fname## how are you today? Hopefully your day is going well. I
+ am the list server for some company, blah blah blah, and I have list
+ed your phone number as ##phone##. Well, here is all the data I have 
+for you:

Name: ##fname## ##lname##
Phone: ##phone##
email: ##email##

So I just wanted to say thank you for signing up yesterday to get emai
+ls from us, and if you don't want to receive any more just click the 
+link below and we won't send any more out. blah blah ~;

my @fields = split( ';', $_mergeFields );
my @recipients = split( '\|', $_list_to_send_to );

foreach my $recipient ( @recipients )
{
    my @recip_data = split( ';', $recipient );
    my $recip_msg = $_message;

    foreach my $field ( @fields )
    {
        my $value = shift @recip_data;
        $recip_msg =~ s/$field/$value/g;
    }

    print $recip_msg, "\n\n";
}
[download]

Note: Don't use this in production - use a templating module.

I'm more of a fan of stuffing the customer info into a hash

the stuff in <readmore> tags is not as interesting

Read more... (628 Bytes)

# trim the # marks 
$_mergeFields =~ s/#//g;
# list of field names                  
my @field_names = split ';', $_mergeFields;
# list of lines from the data
my @records     = split /[|]/, $_list_to_send_to;

my $template = q[
[download]

Read more... (345 Bytes)

];
foreach( @records ) {
    my $message = $template;

    # hash to fill with customer information
    my %customer_record;

    # use a hash slice to populate it, 
    #  we now have keys fname lname email and phone
    @customer_record{ @field_names } = split ';', $_ ;

    # neat, a one line templating engine.
    $message =~ s/##$_##/$customer_record{$_}/g for keys %customer_rec
+ord;

    send_spam $customer_record{email}, $message;

}
[download]

@_=qw; ask f00li5h to appear and remain for a moment of pretend better than a lifetime;;s;;@_[map hex,split'',B204316D8C2A4516DE];;y/05/os/&print;

Update

1. I won't ever use <readmore> tags for code folding again
2. It's nice that my answer is in some way related to the question, as well as TIMTOWTDI

interoffice memo to learn modular arithmetic to----
>myemail@testmail.com
interoffice memo to learn modular arithmetic to----
>email2@testmail.com
interoffice memo to learn modular arithmetic to----
>anothe@test.comn
interoffice memo to learn modular arithmetic to----
>yaea@sendmail.edu
[download]

#! /usr/bin/perl

$_mergeFields="##fname##;##lname##;##email##;##phone##";
$_list_to_send_to=
"Richard;Smith;myemail\@testmail.com;8005551212|
Toby;Johnson;email2\@testmail.com;8885551212|
Chanty;Perkins;another\@test.comn;8665551212|
Eli;Codernaught;yaea\@sendmail.edu;8225551212";

%_merData = ();
%_mergedData = ();

$_field = 0;
while($_mergeFields){
        $_field++;
        ($_tempVar,$_mergeFields)= split /\;/, $_mergeFields,2;
        $_merData{$_field} = $_tempVar;
        print "FieldsStack=$_field:\n".
        "pop \t$_tempVar\n".
        "==Fields stack:$_mergeFields\n";
        }

$_field = 0;
$_recipient_list=0;
while($_list_to_send_to) {
        $_recipient_list++;
        ($_tempVar,$_list_to_send_to) = split /\|/,$_list_to_send_to, 
+2;
        my $_tempMailMessage = $_message;
        my $_tempSubject = $_subject;
        print "\nRecipient Stack:\n$_list_to_send_to\n".
        "pop array:$_tempVar\n";

                while($_tempVar) {
                        $_field++;
                        ($_tempVar2,$_tempVar) = split /\;/, $_tempVar
+, 2;
                        $_mergedData{$_field} = $_tempVar2;
                        print "FieldStack=$_field:\n".
                        "pop \t $_tempVar2\n".
                        "==Fields stack: $_tempVar\n".
                        "-----------------\n";

}}
for $key (keys(%_merData)) {
        $_tempMailMessage =~ s/$_merData{$key}/$_mergedData{$key}/ig;
        $_tempSubject =~ s/$_merData{$key}/$_mergedData{$key}/ig;
        $copykey=$key+1;
        if($_merData{$key} =~ /email##$/) {        $coef=$recipx*$copy
+key;
        $ultrakey=$coef-1;
        $__to=$_mergedData{$ultrakey};
        print "\n\ninteroffice memo to learn modular arithmetic to----
+>$__to\n";
}}}

#go_send_the_message($__to,$_tempSubject,$_tempMailMessage);}

        for $recipx(1...$_recipient_list){
[download]