#!/usr/bin/perl -w

use strict;
use warnings;

use FileHandle;

(my $argact = shift) or die "Syntax:  $0  <fileid>\n";
my $input   = new FileHandle;
my $newfile = new FileHandle;

open($input,   "<", "one.txt") or die "Failed to read 'one.txt' ($!)\n";
open($newfile, ">", "output")  or die "Failed to write 'output' ($!)\n";

while(<$input>){
    s/^Authentication\s+number\s+is\s+(\d+)/Authentication number is $argact/;
    print $newfile "$_";
}

close $input;
close $newfile;