Ted: Sorry about that. I did not put it on my first posting but the first while loop already knows when to execute the sub (when $_ =~ /^$?/). You see, if I run both of those loops independantly from each other (piping the output of one to the second) as in: # cat header.eml | ./first_loop.pl | ./second_loop.pl It works. This is an excersise in Perl programming (with a real purpose...) and I cannot even say (Perl modules) out loud...