my (@pre, @suf);
for (@exclusions) {
  my ($p, $s) = split /ALPHA/, $_, 2;
  push @pre, $p if length $p;
  push @suf, $s if length $s;
}

my $pre_rx = join "", map "(?<!\Q$_\E)", @pre;
my $suf_rx = join "", map "(?!\Q$_\E)", @suf;
my $total_rx = qr/${pre_rx}ALPHA$suf_rx/;