> It's still on the edge to have that $^N involved

Actually you don't really need $^N, since you can test wether $3 is even defined. It makes the code also more robust against the insertion of other match-groups.

The real power tool is the insertion of dynamically evaluated code with (??{... }) and I have to admit that I rarely need this.

use v5.12;
use warnings;
use Test::More;


my $str = '43:1:1; 43:1:2; 43:1:3; 43:1:4; 43:1:5; 43:1:6; 27:3:7; 27:
+3:8; 27:3:9; 65:1:4; 65:1:18';
my $exp = '43:1:1-6; 27:3:7-9; 65:1:4; 65:1:18';

my $got = $str;

$got =~ s(
             ( \d+:\d+: )                    # $1
             ( \d+ )                         # $2
             (?:                             # repeat
                 ;\s                         #   separator
                 \1                          #   head
                 (
                     (??{ ($3//$2) + 1 })    #   insert 1+ ($3 or $2)
                 )                           #   $3 
             )+                              # once or more
         )($1$2-$3)xg;


is( $got, $exp, "fits");

done_testing;

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

In reply to Re^5: Regexp substitution on variable-length ranges with embedded code? (??{...}) by LanX
in thread Regexp substitution on variable-length ranges with embedded code? by Polyglot

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