Ndtyjky

input:
enter image description here

output:
enter image description here

but my out put have one extra white space on last two line.
my output:
enter image description here

my code:

@content = <FILE>; 



foreach $line (@content){ 

    if($line =~ /^#(d+)/){ 

        $number = $1; 

        $line =~ s/^#(d+)/$content[$number-1]/; 

    }

    print "$line"; 

} 

Here's a version of your code with sample input data. If you want people to help you with problems like this, then it's a good idea to make it as easy as possible for them. Posting images of your input data does not make it easy. Also, it's a good development trick to store sample data in the DATA filehandle so that the code and data are together in the same file.

#!/usr/bin/perl



use strict;

use warnings;



my @content = <DATA>;



foreach my $line (@content){

    if($line =~ /^#(d+)/){

        my $number = $1;

        $line =~ s/^#(d+)/$content[$number-1]/;

    }

    print "$line";

}



__DATA__

line A

line B

line C

#7

line D

#2

line E

I've also added use strict and use warnings to your code. In this case, they don't really help, but you should get into the habit of always including them in your Perl programs.

Your problem is here:

$line =~ s/^#(d+)/$content[$number-1]/;

Each of the lines in your @content array will include a newline character at the end. But in this line you're replacing the # symbol and the following digit with a complete other line from the array. You're not replacing the original newline and you're adding another newline (from the replacement string) so the line ends up containing two newlines.

The easiest fix is to add the newline to the pattern you are matching.

$line =~ s/^#(d+)n/$content[$number-1]/;

Note that an experienced Perl programmer would write your code like this:

#!/usr/bin/perl



use strict;

use warnings;



my @content = <DATA>;



for (@content){

    s/^#(d+)n/$content[$1 - 1]/;

    print;

}