Perl 打印关键字上下行

#!/usr/bin/perl 
$dir  = '/home/mysql';
$file = '1.log';
$mon_file = "$dir/$file";
print "$mon_file is $mon_file
";
@warn_arr = qw/连接已关闭 连接超时 NullPointException IndexOutOfBound exception/;
foreach $a (@warn_arr) {
    undef @err_info;
    open( C, "<", "$a.tmp" );
    while (<C>) {
        $count = $_;
    }
    print "$a is $count";

    open( A, "<", "$mon_file" ) || die "$!
";
    $i   = 0;
    $num = 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>) {
            chomp($_);
            push( @err_info, $_ ) if ( $. >= $b - 5 and $. <= $b + 5 );
        }
        print "@err_info is @err_info
";
        system("SMSsendx  111111111 "@err_info" 10.10.10.10");
    }

    open( C, ">", "$a.tmp" );

    print C ("$i
");

}