This is just a curiosity, but why is variable length lookbehind not implemented while variable length lookahead is? Is it because there is no logical need for it, i.e. there is a better way to write a regex that uses it? Or is due to some limitation of how regex can be implemented in perl?
Admittedly, each time I have run into the error writing a quick regex, there has indeed been a better way to write the pattern. To that end, a second question would be has anyone run into a use case where variable length lookbehind would be clearly useful over alternative patterns?
The below is a useless piece of code save only to generate the error.
my $string = 'aaaabcccc';
$string =~ s/(?<=a+)b(?=c+)/B/;
# Variable length lookbehind not implemented in regex m/(?<=a+)b(?=c+)
+/ at C:\Projects\test.pl line 15.