LinuxQuestions.org - Net-Snmp perl scripts failed to open file

Hi,

I am trying to monitor my software RAID1 using snmpd exten command
below is my snmpd.conf file
extend raid-md0 /usr/local/bin/nagios-linux-swraid.pl --device=md0
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root@localhost]snmpwalk -v2c -c public 127.0.0.1 NET-SNMP-EXTEND-MIB::nsExtendOutputFull

NET-SNMP-EXTEND-MIB::nsExtendOutputFull."raid-md0" = STRING: Can't open /proc/mdstat : Permission denied at /usr/local/bin/nagios-linux-swraid.pl line 56.
=======================
IT gives me permission denied opening file. File permission is r--r--r.
Attached sample scripts:
#!/usr/bin/env perl

# Get status of Linux software RAID for SNMP / Nagios
# Author: Michal Ludvig <michal@logix.cz>
# http://www.logix.cz/michal/devel/nagios
#
# Simple parser for /proc/mdstat that outputs status of all
# or some RAID devices. Possible results are OK and CRITICAL.
# It could eventually be extended to output WARNING result in
# case the array is being rebuilt or if there are still some
# spares remaining, but for now leave it as it is.
#
# To run the script remotely via SNMP daemon (net-snmp) add the
# following line to /etc/snmpd.conf:
#
# extend raid-md0 /root/parse-mdstat.pl --device=md0
#
# The script result will be available e.g. with command:
#
# snmpwalk -v2c -c public localhost .1.3.6.1.4.1.8072.1.3.2

use strict;
use Getopt::Long;

# Sample /proc/mdstat output:
#
# Personalities : [raid1] [raid5]
# md0 : active (read-only) raid1 sdc1[1]
# 2096384 blocks [2/1] [_U]
#
# md1 : active raid5 sdb3[2] sdb4[3] sdb2[4](F) sdb1[0] sdb5[5](S)
# 995712 blocks level 5, 64k chunk, algorithm 2 [3/2] [U_U]
# [=================>...] recovery = 86.0% (429796/497856) finish=0.0min speed=23877K/sec
#
# unused devices: <none>

my $file = "/proc/mdstat";
my $device = "all";

# Get command line options.
GetOptions ('file=s' => \$file,
'device=s' => \$device,
'help' => sub { &usage() } );

## Strip leading "/dev/" from --device in case it has been given
$device =~ s/^\/dev\///;

## Return codes for Nagios
my %ERRORS=('OK'=>0,'WARNING'=>1,'CRITICAL'=>2,'UNKNOWN'=>3,'DEPENDENT'=>4);

## This is a global return value - set to the worst result we get overall
my $retval = 0;

my (%active_devs, %failed_devs, %spare_devs);

open FILE, "< $file" or die "Can't open $file : $!";

while (<FILE>) {
next if ! /^(md\d+)+\s*:/;
next if $device ne "all" and $device ne $1;
my $dev = $1;
====================REST is scraped================