use strict;
my $str = '/post/cho-minh-hoi-voi-kien-thuc-ve-cc-va-sql-o-truong-dai-hoc-da-du-de-thuc-tap-chua-vay-moi-nguoi-minh-2131321-nghe-may-nguoi-da-tot-nghiep-noi-la-luc-di-lam-nguoi-ta-ko-dung-nhung-kien-thuc-trong-truong-dai-1321321321';
my $regex = qr/^\/topic\/(?:.+-)*(\d+)/mp;
if ( $str =~ /$regex/g ) {
print "Whole match is ${^MATCH} and its start/end positions can be obtained via \$-[0] and \$+[0]\n";
# print "Capture Group 1 is $1 and its start/end positions can be obtained via \$-[1] and \$+[1]\n";
# print "Capture Group 2 is $2 ... and so on\n";
}
# ${^POSTMATCH} and ${^PREMATCH} are also available with the use of '/p'
# Named capture groups can be called via $+{name}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html