I agree in principle, although it's not really related to configuring VirtualHosts so it would probably deserve to be discussed in a node of its own.

...By someone considerably more skilled than myself :-/

I worked around the problem by scanning the passwd/group files manually. Not at all portable ofcourse, but that's no particular concern of mine.

my %users = ();
my %groups = ();

my $pfname = '/etc/passwd';
open(my $pfh, $pfname) || warn "Error reading $pfname: $!";
while (my $line = <$pfh>) {
  my ($name) = split(/:/, $line);
  $users{$name} = 1;
}
close $pfh;

my $gfname = '/etc/group';
open(my $gfh, $gfname) || warn "Error reading $gfname: $!";
while (my $line = <$gfh>) {
  my ($name) = split(/:/, $line);
  $groups{$name} = 1;
}
close $gfh;
[download]

When getpwent returns undef, what is output of sub Fudge?

Let's see, I inserted the following into my Apache conf perl section:

while ( my $user = getpwent() ) { $users{$user} = 1; }
while ( my $group = getgrent() ) { $groups{$group} = 1; }
open (my $fh, '>>', '/var/log/httpd/fudge.log');
print $fh Fudge();
close $fh;

sub Fudge {
    use Errno();
    join qq/\n/,
      "Error @_",
      map { "  $_" } int( $! ) . q/ / . $!,
      int( $^E ) . q/ / . $^E,
      grep( { $!{$_} } keys %! ),
      q/ /;
}
[download]

Here's what I got after restarting httpd:

Error 
  25 Inappropriate ioctl for device
  25 Inappropriate ioctl for device
  ENOTTY
Error 
  25 Inappropriate ioctl for device
  25 Inappropriate ioctl for device
  ENOTTY
[download]

All I can tell from this is that the config is indeed executed twice (as mentioned in the OP) but the actual messages don't mean much to me.

If I had a gun pointed at me and had to guess, I'd say it has something to do with the environment presented to httpd by systemd.

-- FloydATC

Time flies when you don't know what you're doing