I also could not get this !// thing to work in the grep. I am mystified why it doesn't, but I did recode according to Flipin good, or a total flop? which tests the value of the flip-flop regex and this does work in a grep. Just a point of reference: 
#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my @list= ("a".."c","DBIC","A".."C","DANCER","a".."c");

my @result;
for (@list) { push @result,$_ if /DBIC/.. /DANCER/ and ! // }

print Dumper \@result;

# uses http://www.perlmonks.org/?node_id=525392
my @result2 = grep { (/DBIC/.. /DANCER/)  =~ /^\d+(?<!^1)$/ }@list;
 
print Dumper \@result2;

__END__
$VAR1 = [
          'A',
          'B',
          'C'
        ];
$VAR1 = [
          'A',
          'B',
          'C'
        ];

[download]
The value of the flip-flop regex returns a line number like: 1,2,3,4E0 and that number can be tested in another regex.

As another note this "xE0" notation is used in other places in Perl. For example, the DBI can return 0E0 as the number of results which is 0 * 10**0 or numeric zero (0 * 1) although this evaluates to "true" when tested in a logical sense, meaning that that the statement "worked" but returned no results (numeric value is zero). Here the line number ending in E0 is the "last one". This is clever but it works.

In reply to Re: Bug with "last successfully matched regular expression" (empty regex) by Marshall
in thread Bug with "last successfully matched regular expression" (empty regex) by LanX

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