perl 没有关键文件句柄引起的逻辑错误

<pre name="code" class="sql">flow02:/home/tomcat> cat m1.pl 
#!/usr/bin/perl 
use POSIX;
my $dir  = '/home/tomcat';
my $file = '1.log';
$mon_file = "$dir/$file";
my $SDATE = strftime("%Y%m%d%H%M%S",localtime());
$UPLOADPATH = "/data/swap/mbanklog/$IPMACHINE-$SDATE$file";
##########监控关键字，以空格隔开################
@warn_arr = qw/Exception 555/;
foreach $a (@warn_arr) {
    undef @err_info;
    open( C, "<", "$a.tmp" );
    while (<C>) {
        $count = $_;
    }
print "=========================================================================================================================
";
print "######监控异常关键字：      "$a"---数量=$count
";
    open( A, "<", "$mon_file" ) || die "$!
";
    $i   = 0;
    $num = 0;
    $b = 0;
    while (<A>) {
        $num++;
        if ( $_ =~ /$a/i ) { $i++; $b = $num }
    }
    print "######$b is $b######
";
        if ( $i != 0 && $i == $count && defined($count) ) {
        open( B, "<", "$mon_file" ) || die "$!
";
        while (<B>) {
        if  (($. >= "$b" -2) and  ($. <= "$b" + 2) ){push( @err_info, $_ ) };
        };
        print "######@err_info is   @err_info
";
#close B;
    }
    open( C, ">", "$a.tmp" );
    print C ("$i
");
}


flow02:/home/tomcat> cat 1.log 
4444
2223
5555
java.lang.NullPointerException]
4
java.lang.NullPointerException
5
8


flow02:/home/tomcat> perl m1.pl 
=========================================================================================================================
######监控异常关键字：      "Exception"---数量=2

$i is 2
$b is 6
######$b is 6######
######@err_info is   java.lang.NullPointerException]
 4
 java.lang.NullPointerException
 5
 8

=========================================================================================================================
######监控异常关键字：      "555"---数量=1

$i is 1
$b is 3
######$b is 3######
######@err_info is    ###这个地方没有打印第3行的上下2行,为什么呢？

$i 表示匹配关键字的次数



产生原因为没有关键文件句柄B;

flow02:/home/tomcat> perl m1.pl 
=========================================================================================================================
######监控异常关键字：      "Exception"---数量=2

$i is 2
$b is 6
######$b is 6######
######@err_info is   java.lang.NullPointerException]
 4
 java.lang.NullPointerException
 5
 8

=========================================================================================================================
######监控异常关键字：      "555"---数量=1

$i is 1
$b is 3
######$b is 3######
######@err_info is   4444
 2223
 5555
 java.lang.NullPointerException]
 4

为什么呢？没有关闭文件句柄,行号累加了。

flow02:/home/tomcat> perl m1.pl 
=========================================================================================================================
######监控异常关键字：      "Exception"---数量=2

$i is 2
$count is 2

######$b is 6######
$. is 1
$. is 2
$. is 3
$. is 4
$. is 5
$. is 6
$. is 7
$. is 8
######@err_info is   java.lang.NullPointerException]
 4
 java.lang.NullPointerException
 5
 8

=========================================================================================================================
######监控异常关键字：      "555"---数量=1

$i is 1
$count is 1

######$b is 3######
$. is 9
$. is 10
$. is 11
$. is 12
$. is 13
$. is 14
$. is 15
$. is 16
######@err_info is