perl 获取更新部分日志

#!/usr/bin/perl
#取文件行数
##循环开始清空文件
if (-f "tmp.out"){
open FILE,">tmp.out";
close FILE;}

open( A, "<", "count.txt" );
            while (<A>) {
            $count = $_;
                        };
print "上次记录的记录数为$count
";


open(my $fh, '<', 'catalina.out');
$. = 0;
while (<$fh>) {
    ($num=$.) if eof;
};
print "文件最新的记录数为$num"."
";
    open( B, ">", "count.txt" );
    print B ("$num
");

if ( defined($count)  && $num != $count && $num !=0  )
{print "开始处理
";
     open( C, "<", "catalina.out" ) || die "$!
";
       while (<C>) {
             if  ($. > "$count" ){ 
              open( D, ">>", "tmp.out" );
              print D ("$_
");
             }
}};