#!/usr/bin/perl
#
# given a file name as an argument,
# read the file until eof, back up
# one line and truncate the file there.
# in short, "delete the last line of a file"
#
my $file=shift(@ARGV);
open(FILE,"+<$file") or die;
while (<FILE>) {
    if (eof(FILE)) {
       seek(FILE,-(length($_)),2) or die;
       truncate(FILE,tell(FILE)) or die;
    }
}
close FILE;