On Thu, 9 Jan 2020 at 05:49, Joseph He <joseph.he.2...@gmail.com> wrote:
>
> I think $str =~ /(\d+)\s(\d+)\s(??{$1*$2})/ should do it
> My Perl version is v5.26.1
I think you mean (??{ "$1*$2"}) which might work, but it will be error
prone, (??{"(?$1)*$2") would be better, but both will be slow, as each
time a new pattern willbe compiled.
/(\d+)\s(\d+)\s(\1*\2)/
just works, and does not recompile the pattern over and over. Look for
"back references" in perlre.
Yves
