Hello Akatsuki, and welcome to the Monastery!

It looks like your data may be in CSV (comma-separated values) format. If so, you will be better off (in the long run) to parse it with a dedicated module rather than a regular expression. For example, the following code uses Text::CSV_XS to read the values, then it doubles those which are decimal numbers but leaves the others unchanged:

use strict;
use warnings;
use Text::CSV_XS;

my $csv    = Text::CSV_XS->new({ allow_whitespace => 1 });
my $string = '"", "2.90", "3.00", "3.10", "3.20", "3.30", "3.40", "3.5
+0", ' .
         '"3.60", "3.70", "3.80", "3.90", "4.00", "4.10", "4.20", "5v"
+';

if ($csv->parse($string))
{
    my @fields = $csv->fields;
    /(\d+\.\d+)/ && ($_ *= 2) for @fields;
    print "$_\t" for @fields;
}
else
{
    $csv->error_diag();
}
[download]

Output:

 0:12 >perl 1707_SoPW.pl
        5.8     6       6.2     6.4     6.6     6.8     7       7.2   
+  7.4
7.6     7.8     8       8.2     8.4     5v
 0:12 >
[download]

Hope that helps,

Thank you for your answer, but I think I have expressed myself wrong so I will post my entire code If you can help me. I want to open a file, read the values between the double quotes and replace some numbers from this file with their corresponding value from the first line. This is my code:

#!/usr/bin/perl
# matchtest2.plx
use warnings;
use strict;

open (my $original, '<', 'data.txt') or die $!;
open (my $fh, '>', 'output.txt') or die $!;

while (my $line = <$original>) {

if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/) {
    my $replace = $1;
    $line =~ s/[^.]00/$replace/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace1 = $2;
    $line =~ s/01/$replace1/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace2 = $3;
    $line =~ s/02/$replace2/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace3 = $4;
    $line =~ s/03/$replace3/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace4 = $5;
    $line =~ s/04/$replace4/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace5 = $6;
    $line =~ s/05/$replace5/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace6 = $7;
    $line =~ s/06/$replace6/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace7 = $8;
    $line =~ s/07/$replace7/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace8 = $9;
    $line =~ s/08/$replace8/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace9 = $10;
    $line =~ s/09/$replace9 /g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace10 = $11;
    $line =~ s/[^.]10/$replace10/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace11 = $12;
    $line =~ s/11/$replace11/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace12 = $13;
    $line =~ s/12/$replace12 /g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace13 = $14;
    $line =~ s/13/$replace13/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace14 = $15;
    $line =~ s/14/$replace14/g;
}
if ($line =~ m/\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", 
+\"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(
+.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\", \"(.*?)\"/g) {
    my $replace15 = $16;
    $line =~ s/15/$replace15/g;
}

print {$fh} $line;
}
close $original;
close $fh;
[download]

and this is my original file(just a short version, the actual one has thousands of numbers)

"", "2.90", "3.00", "3.10", "3.20", "3.30", "3.40", "3.50", "3.60", "3
+.70", "3.80", "3.90", "4.00", "4.10", "4.20", "5v"
09    12    12    10    08    08    10    07    10    09    08    08  
+  06    10    10    08    09    11    08    10    07    10    11
00    00    10    12    13    10    09    08    08    06    10    01  
+  08    09    11    08    10    07    10    11    12    13    05
[download]

I have to replace for example 00 with the value between the first "" so 00 would be empty string, 01 with the value of the second "2.90" so 01 would become 2.9 and so on... Thank you very much for all your help

Did you look at my previous suggestion regarding the "g" regex modifier? Here's how to use it:

#!/usr/bin/env perl 
use strict;
use warnings;

open (my $original, '<', 'data.txt') or die $!;
open (my $fh, '>', 'output.txt') or die $!;

my $first = <$original>;
print $fh $first;
my @replace = $first =~ /"([^"]*)"/g;

while (my $line = <$original>) {
    $line =~ s/(\d{2})/$replace[$1]/g;
    print $fh $line;
}

close $original;
close $fh;
[download]

Is that concise enough for you?

Have a look at "g" in Regex Modifiers.

Here's one way how to change the format of the lines:

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

$_ = '"", "2.90", "3.00", "3.10", "3.20", "3.30", "3.40", "3.50", "3.6
+0", "3.70", "3.80", "3.90", "4.00", "4.10", "4.20", "5v"';
my $regex  = join ', ', map '"(.*?)"', 1 .. 16;
my $string = join '|',  map qq(<$_>), /$regex/;
say length $string ? $string : $_;
[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]

I think a Text::CSV approach as outlined by Athanasius here might be better in general, but if you're stuck with using regexes, here's another approach.

I'm also stumped by the "replace by what?" question, so this solution just uses a list of one-for-one replacement strings. Note that due to the arcane demands of Windose, what appears as  [^^\"] below is really the  [^"] complemented character set, and  \" is really  " for the same reason. Note also that Perl version 5.10+ is needed due to the use of the  \K operator; I think a work-around would be | a work-around is fairly simple for pre-5.10 Perls.

c:\@Work\Perl\monks>perl -wMstrict -le
"use 5.010;
 ;;
 my $old =
   '\"\", \"2.90\", \"3.00\", \"3.10\", \"3.20\", \"3.30\", \"3.40\", 
+\"4.20\", \"5v\"';
 print qq{'$old'};
 ;;
 my @repl = ('', qw(9.11 9.21 9.31 9.41 9.51 9.61 9.71 6wxyz));
 my $new = replace_from_list($old, @repl);
 print qq{'$new'};
 ;;
 ;;
 sub replace_from_list {
   my ($string, @list) = @_;
   ;;
   my $i = 0;
   $string =~ s{ \G (?: \" , [^^\"]*)? \" \K [^^\"]* (?= \") }
               {$repl[ $i++ ]}xmsg;
   $i == @list or die qq{replacement list mismatch};
   return $string;
   }
"
'"", "2.90", "3.00", "3.10", "3.20", "3.30", "3.40", "4.20", "5v"'
'"", "9.11", "9.21", "9.31", "9.41", "9.51", "9.61", "9.71", "6wxyz"'
[download]