#!/usr/bin/perl
use Modern::Perl; #does an implict use strict; use warnings and activates "new" features
no warnings qw /uninitialized/;

my @result; # declares the array we will use to store the results

{ # starts a block
    open my $INPUTFILE, '<', '/Users/ts/numbers.txt' or die "File error: input file: $!";
    while (<$INPUTFILE>) {
        chomp; #removes new line
        my ($index, $value) = split /\t/; # splits each record at the tab "\t" -character
        $result[$index] = $value; # and store the value in the array at the right place
    }
} # ends the block, $INPUTFILE goes out of scope and closes the filehandle automatically

$result[3000050] = 0 unless $result[3000050];

{ # starts a block
    open my $OUTPUTFILE, '>', '/Users/ts/full_number.txt'or die "File error: output file: $!";
    while (my ($index, $value) = each @result) {
        next if $index == 0;
        say $OUTPUTFILE, "$index\t", $value+0; # saves the results in a >>indexnumber tab value<< format
    }
} # ends the block, $OUTPUTFILE goes out of scope and closes the filehandle automatically