I don't have a good idea of your difficulties, but here's a generalized approach. I can't provide a working example at the moment, so the following is untested handwaving.

The  (*SKIP)(*FAIL) variable-width negative look-back hack works by messing up a match of something you need to have for an overall match. For a large regex, I tend to take the approach of factoring regex elements:

# stuff we want to capture
my $capture_this = qr{ ... }xms;
my $capture_too  = qr{ ... }xms;
my $capture_also = qr{ ... }xms;
my $capture_more = qr{ ... }xms;

# stuff we want to cause match failure if before certain other stuff
my $avoid_this = qr{ ... }xms;
my $avoid_too  = qr{ ... }xms;
my $avoid_also = qr{ ... }xms;
my $negatory   = qr{ (?> [aeiou]+ | f[eio]e? | $avoid_too) }xms;

# stuff we need for an overall match, may or may not be captured
my $needed_for_match = qr{ ... }xms;
my $needed_too       = qr{ ... }xms;

my $string = get_stringy_stuff();

my ($this, $too, $also, $yet_another) = $string =~ m{
    \A
    ($capture_this)
    ($capture_too)
    ...
    (?> (?> $avoid_this | $avoid_too | $avoid_also | etc) $needed_for_
+match (*SKIP)(*F))?
    $needed_for_match  # needed for overall match
    ($capture_also)
    ...
    (?> $negatory $needed_too (*SKIP)(*FAIL))?
    ($needed_too)  # needed for overall match, also captured
    \z                                 
    }xms;

do_something_with($this, $too, $also, $yet_another);
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