Assign regex match to variable in while loop

[Clemens Bieg]

Hello,

I am trying to iterate over all the lines of a file, each of which starts
with a line number, and isolate the line number and the corresponding string
into one variable each, then have them printed into a separate file. Could
someone give me a clue on how to assign the line number match to the
variable so I can reuse it? Here is what I am trying (mainly by analogy with
examples I found on the web and in books, but I am lacking the background
knowledge). At this point, all I am trying is to see if I can get the line
number into a variable, and print it out.


use strict;
use warnings;
my ($qfn_in_extract) = "extract/extract.txt";
my ($qfn_in_allnumbered) = "extract/allnumbered.txt";
my $dir = mkdir("final");

open(my $fh_in_extract, '<', $qfn_in_extract)
   or die("Unable to read file \"extract.txt\": $!\n");
open(my $fh_in_allnumbered, '<', $qfn_in_allnumbered)
   or die("Unable to read file \"allnumbered.txt\": $!\n");
open(my $fh_out_final, '>', "final/final.txt")
   or die("Unable to create file \"final.txt\": $!\n");

my $id = '';

while (<$fh_in_extract>) {

   if ($id = m/^\d+/) {
   print $fh_out_final $id;
   }
}

#   my $string = m/(?<=\d ).*?$/;
#   print $fh_out_final $_;


This only gives me the return status. I have been playing with and without
the if statement, with and without the $id variable, with $_ instead of $id,
and with =~ instead of =.  But I do not see the light... I would appreciate
if someone could point me in the right direction.

Clemens