#!/perl/bin/perl.exe -w

use strict;
use vars qw($cur_pos $buf);

my $file = $ARGV[0];

open my $fh, "+<$file" or die "$!";

    my $size = 4096;

    seek $fh, -$size, 2;
    while (1) {
	$cur_pos = tell $fh;
	read $fh, $buf, $size;
	last if $buf =~ m/\S/s;
	seek $fh, -$size*2, 1;
    }

    $buf =~ m/(\s*)$/s;
    $cur_pos += $-[0] || 0;

    truncate $fh, ++$cur_pos if $cur_pos;

    close $fh;