Re: how to run regex calculation

It probably won't ever work.  The problem is the * (star/asterisk) after 
\1 is being interpreted in the context of regular expressions, ie, 
"zero-or-more matches", and not as a multiplication operator.  In fact,

~]$ perl -Mstrict -le 'my $str = "2 3 23"; print "true" if 
$str=~/(\d+)\s(\d+)\s(\1*\2)/'

...does indeed print "true"

It would probably make the most sense to not try to do this as a 
one-liner (why do we perl programmers love to be cute like that?), and 
simply break it up into two steps:

$str =~ s/(\d+)\s(\d+)\s(\d+)/;
print "true" if ($1*$2 == $3);

- Michael



On 1/9/2020 12:39 AM, Wesley Peng wrote:
> Hallo
>
> on 2020/1/9 16:35, demerphq wrote:
>> $str=~/(\d+)\s(\d+)\s(\1*\2)/
>>
>> $1 refers to the capture buffers from the last completed match, \1
>> inside of the pattern part of a regex refers to the capture buffer of
>> the currently matching regex.
>
> This doesn't work too.
>
> perl -Mstrict -le 'my $str = "2 3 6"; print "true" if 
> $str=~/(\d+)\s(\d+)\s(\1*\2)/'
>
> nothing printed.
>
>
> Regards.