Use "use Fcntl ':mode';" to import S_I* constants. They are just bitmasks that masks bits from portions of files permissions. In Unix systems they are grouped into 4 groups of 3 bits. First three are for setuid(4), setgid(2), stickybit(1). Other three groups of bits are for user, owner group and others. Permissions are read(4), write(2) and execute(1).

Permissions are often represented in octal form, so for this permission "rwxr-x-w-" you will have octal one 0752.

I recommend you reading "perldoc -f stat" document, you have it all there. Except some of the stuff about inner working, which you could find in "info glibc" if you are working on some Linux system.

#!/usr/bin/env perl

use Fcntl ':mode';

use strict;
use warnings;

my $mode = (stat($ARGV[0]))[2];

my $user_rwx      = ($mode & S_IRWXU) >> 6;
my $group_read    = ($mode & S_IRGRP) >> 3;
my $other_execute =  $mode & S_IXOTH;

printf "Permissions are %04o\n", S_IMODE($mode), "\n";

my $is_setuid     =  $mode & S_ISUID;
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perl -e 'use Fcntl qw(:mode);$permissions=S_IMODE((stat("filename"))[2
+]);print $permissions,"\n";'
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Sorry!Utilitarian I just given the hint, and missed something,Below the code I just tried,

 use Data::Dumper;
use Fcntl ':mode';

my $filename="pl_bak.pl";
my @array=lstat($filename);
$permissions = sprintf "%04o", S_IMODE($array[2]);
print "File permissions: $permissions\n";
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Update

Removed a file type line.