Hello,

I want solve this problem using regexes:
Given a "sorted" target string and a sequence of sizes of groups of equal consecutive characters, find and output characters from a string which corresponds to each group.

I wrote a code, which glues smaller regexes to a bigger one, and uses re-eval ((?{ ... })). I use a "stack" array for saving captured characters, and use push/pop to manipulate it.
Also I used $^N variable interpolating it inside double-quotes. This fails to run without "use re 'eval'". How can I overcome it? Any alternatives to $^N for access a last captured group outside of regex?
Any ideas of alternative solutions for a given problem? Code:
#!/usr/bin/perl

use warnings;
use strict;
use re 'eval';

$\ = $/;

while(<DATA>){
    print '-' x 15;
    
    chomp;
    
    my $target = $_;
    my @groups = split ' ', <DATA>;
    
    print "target:[$target]";
    print "groups:[@groups]";
    
    my @chars_seq;
    
    my $re = join " (?!\\g{-1}).*? \n", 
        map { sprintf 
            "(?: " . 
                "( (.)\\g{-1}{%d} ) " .
                "(?{ push \@chars_seq, \$\^N; }) " .
                "(?: (?=) | (?{ pop \@chars_seq }) (*FAIL) ) " . 
                "(?{ print join ' ', \@chars_seq; })" .
            ")"
            , $_ - 1
            } @groups;
    
    print for "regex:[",
        $re,
        "]";
    
    $re =~ s/\n//g;
    
    $target =~ /
        $re
        /x or print "FAIL!";
    
    print "character sequence:[@chars_seq]";
    }

__DATA__
cbaa
1 2
cba
1
bbaa
1 2
cccqrrtaaa
2 2 2
cccqrrtaaa
1 1 2 2
cccqrrtaaa
1 1 1 1 3

[download]
OUTPUT: 
---------------
target:[cbaa]
groups:[1 2]
regex:[
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{1} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; }))
]
c
c aa
character sequence:[c aa]
---------------
target:[cba]
groups:[1]
regex:[
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; }))
]
c
character sequence:[c]
---------------
target:[bbaa]
groups:[1 2]
regex:[
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{1} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; }))
]
b
b
b aa
character sequence:[b aa]
---------------
target:[cccqrrtaaa]
groups:[2 2 2]
regex:[
(?: ( (.)\g{-1}{1} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{1} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{1} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; }))
]
cc
cc
cc rr
cc rr aa
character sequence:[cc rr aa]
---------------
target:[cccqrrtaaa]
groups:[1 1 2 2]
regex:[
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{1} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{1} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; }))
]
c
c
c
c q
c q rr
c q rr aa
character sequence:[c q rr aa]
---------------
target:[cccqrrtaaa]
groups:[1 1 1 1 3]
regex:[
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{0} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; })) (?!\g{-1})
+.*? 
(?: ( (.)\g{-1}{2} ) (?{ push @chars_seq, $^N; }) (?: (?=) | (?{ pop @
+chars_seq }) (*FAIL) ) (?{ print join ' ', @chars_seq; }))
]
c
c
c
c q
c q r
c q r
c q r t
c q r t aaa
character sequence:[c q r t aaa]

[download]

In reply to How to access last capture groups outside regex using interpolation but w/o using re 'eval'? by rsFalse

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.