#!/usr/bin/perl

use strict;
use warnings;

sub get_next_number {
	open FILE, "<$0" or die "1:Could not open file : $!\n";

	my @lines = <FILE>;
	my $n = $1 if ( @lines[scalar @lines - 1] =~ /#NEXT_UID=(\d+)/ );
	my $m = $n + 1;
	pop @lines;
	push @lines, "#NEXT_UID=$m\n"; 
	close (FILE);

	open FILE, "+<$0" or die "2:Could not open file : $!\n";
	print FILE $_ foreach @lines; 	
	close (FILE);	
	return $n;	
}

my $num;
$num = get_next_number();
print "Next available number is : $num\n";

$num = get_next_number();
print "Next available number is : $num\n";

#NEXT_UID=14