use warnings;
use strict;
use File::stat;
use Fcntl qw/S_IMODE/;

my $filename = $0; # just for testing
my $stat = stat($filename) or die "stat $filename: $!";
my $perms = S_IMODE($stat->mode);
printf "%#0o\n", $perms;
chmod $perms, $filename or die "chmod $filename: $!";