#!/usr/bin/perl
$_ = 'Patron @FirstName@ @LastName@ has filled out the @FormName@ form
+. Please send them an email at @EmailAddress@.';

s/@([a-zA-Z]+?)@/<b>\@$1\@<\/b>/g;

print $_ . "\n";
# Output: Patron <b>@FirstName@</b> <b>@LastName@</b> has filled out t
+he <b>@FormName@</b> form. Please send them an email at <b>@EmailAddr
+ess@</b>.
[download]

This gets the right output with the sample data you gave. I hope it helps you along.

--
Allolex

Update 2003-08-06 15:28:15 CEST: Fixed substitution problem pointed out by Abigail-II (Thanks!).