use warnings;
use strict;
use diagnostics;

my $database = "Database.txt";
my $part_number_range = 10;

open (my $input, "<" , $database) || die "Can't open $database: $!";
my %part_numbers = map { chomp; $_=>1 } <$input>;
close $input;

use Data::Dumper; print Dumper(\%part_numbers); # DEBUG

my $new_part_number;
my $bail_out_count;
while (1) {
	$new_part_number = sprintf("%07d", int(rand($part_number_range)));
	last unless exists $part_numbers{$new_part_number};
	die "Bailing out after too many retries" if ++$bail_out_count>1000;
	print "Collision with part number '$new_part_number', retrying\n"; # DEBUG
}

print "Chose part number: '$new_part_number'\n"; # DEBUG

open (my $output, ">>" , $database) || die "Can't open $database: $!";
print $output "$new_part_number\n";
close $output;