This is regarding regex backreference.

I'm not sure you're using the right terminology, but here's an example in which a regex with a backreference is entered, matches and captures: 

>perl -wMstrict -le
"$_ = '1:A silly sentence (495,a), silly but useful.(3)';
 ;;
 print 'Enter a regular expression:';
 my $expression = <STDIN>;
 chomp($expression);
 print qq{expression is '$expression'};
 ;;
 if (/$expression/) {
   print 'The expression matches the string';
   print qq{\$1 is '$1'} if defined $1;
   print qq{\$2 is '$2'} if defined $2;
   print qq{\$3 is '$3'} if defined $3;
   }
 else {
   print 'The expression does not match';
   }
"
Enter a regular expression:
(\w+).*(\1)
expression is '(\w+).*(\1)'
The expression matches the string
$1 is 'silly'
$2 is 'silly'

[download]

See discussion of backreferences in Capture groups in perlre.

In reply to Re: Regex backreference by AnomalousMonk
in thread Regex backreference by vyeddula

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