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### Re^2: Regular expressions: interpolate the variable in the value of the number of repetitions for the group

by 0day (Sexton)
 on Aug 03, 2013 at 05:47 UTC ( #1047674=note: print w/replies, xml ) Need Help??

Heh... Thanks, but I want to do it the forces of the regular
expression (without external code).

Problem has practical examples (which are easily solved by
external code), but I want to do it other way.

Thanks.
• Comment on Re^2: Regular expressions: interpolate the variable in the value of the number of repetitions for the group

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Re^3: Regular expressions: interpolate the variable in the value of the number of repetitions for the group
by rjt (Deacon) on Aug 03, 2013 at 10:29 UTC
Heh... Thanks, but I want to do it the forces of the regular expression (without external code).

The really funny thing is, all of the broken examples you cite as somehow desirable in the root node execute "external code" (which I take to mean non-regex Perl code), via the experimental features (?{ ... }) and (??{ ... }):

0day's code:

```\$binary_data =~ /(.)(.){(?{unpack 'H*', \$1})}/; # ?
/(.)(?{unpack 'H*', \$1})(.){\$^R}/; # ???
/(.)((??{'.' x \$1}))/;
/(\d)((??{'.*?\n' x \$1}))/;

how to assign a value aaaa\n of \$3, bbbb\n -> \$4 etc ?

Short answer: you can't, unless you're OK with this:

```/(\d) ([^\d]+?\n)? ([^\d]+?\n)? ([^\d]+?\n)?
([^\d]+?\n)? ([^\d]+?\n)? ([^\d]+?\n)?
([^\d]+?\n)? ([^\d]+?\n)? ([^\d]+?\n)? /x;
printf "%d: <%s>\n", \$_, eval '\$'.\$_ for 2..\$1+1;

But, no doubt you already thought of that. I want to help you, and to do that, I need a complete description of the actual problem you're trying to solve that you need our help with, as well as some real examples of input and expected output.

Re^3: Regular expressions: interpolate the variable in the value of the number of repetitions for the group
by Laurent_R (Canon) on Aug 03, 2013 at 09:41 UTC

I do not know whether the solution proposed by rjt solves your problem, because you haven't decribed your problem and your data in sufficient details, but rjt's solution does not use any external code, but just Perl core functions and operators. And, BTW, the split function uses regular expressions.

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