Well, your talk of complexity later on included; build it w/ the debug in and a non-mailing mode:

print MAILPIPE 'blah $blah' if $mailing;
print STDERR "trying MAILPIPE 'blah $blah'\n"
  if $debug > 30;
[download]

so you can $mailing = 0; $debug =40; and get stderr and no mail. Just keep your debug in line w/ your MAILPIPE data as the code evolves.

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