use MIME::Base64;

my $cstr = 'dwAgAEMAcgBlAGQAaQB0ACAAQwBhAHIAZAAgAEMAbwB1AGwAZAAgAEIAZQAgAEgAZQBhAGQAZQBkACAAWQBvAHUAcgAgAFcAYQB5AA';

my $chk = decode_base64($cstr);
print "$chk\n";