Another variation:

c:\@Work\Perl\monks>perl -wMstrict -le
"my $path = 'XX.YY.ZZ';
 my ($ignore) =
   map qr{ (?: $_) (?! [[:alpha:]]) }xms,
   join q{ | },
   qw(if while for)
   ;
 ;;
 my $s = '(ABC | (~dEf & hIJ)) & ~LMn if form while i';
 ;;
 my $expected = '(XX.YY.ZZ.ABC | (~XX.YY.ZZ.dEf & XX.YY.ZZ.hIJ)) & ~XX
+.YY.ZZ.LMn if XX.YY.ZZ.form while XX.YY.ZZ.i';
 print qq{expected: '$expected'};
 ;;
 $s =~ s{ (?<! [[:alpha:]]) (?= [[:alpha:]]) (?! $ignore) }
        {$path.}xmsg;
 print qq{     got: '$s'};
 $s eq $expected or die 'FAILED';
 print 'a-ok';
"
expected: '(XX.YY.ZZ.ABC | (~XX.YY.ZZ.dEf & XX.YY.ZZ.hIJ)) & ~XX.YY.ZZ
+.LMn if XX.YY.ZZ.form while XX.YY.ZZ.i'
     got: '(XX.YY.ZZ.ABC | (~XX.YY.ZZ.dEf & XX.YY.ZZ.hIJ)) & ~XX.YY.ZZ
+.LMn if XX.YY.ZZ.form while XX.YY.ZZ.i'
a-ok
[download]

(Long lines: Beware linewrap.)

Update: Just took another look at Re^2: Appending strings and realized solution above doesn't cover "1'b0" or "ABC_DEF". These could be included, but I'm sure that wouldn't be the end of it. Yeah, a real Verilog parser looks like the best bet.