G'day chandantul,

You should check perldiag when you encounter an error message that you don't understand. In this instance, "Modification of a read-only value attempted" describes a number of situations in which this particular message may be emitted.

If that information doesn't help, you should provide us with an SSCCE that reproduces your problem. In many cases, the process of writing an SSCCE will identify the problem for you. A single line of code, with no context, does not help us to help you.

Please also read: "How do I post a question effectively?".

That's supposed to be the line causing this error?

No way...

Help us to help you by providing more insight.

update

the only possibility I see is auto-vivification of non existent entry "creden" provided $response[$i][$j] is read-only. (if that's even possible)

A prior check would solve this!

update

though the error messages don't match.

  DB<72> $a{1}=\1

  DB<73> use warnings; say $a{1}{foo}{bar}
Not a HASH reference at (eval 81)[c:/Perl_524/lib/perl5db.pl:737] line
+ 2.
[download]

So I was able to reproduce it

  DB<75> use Readonly;

  DB<77> Readonly::Hash    %has => (key1 => 1, key2 => 2 );

  DB<78> x \%has
0  HASH(0x332b388)
   'key1' => 1
   'key2' => 2
  DB<79> $a{1}=\%has

  DB<80> use warnings; say $a{1}{foo}{bar}
Modification of a read-only value attempted at (eval 94)[c:/Perl_524/l
+ib/perl5db.pl:737] line 2.

  DB<81>
[download]

you must check if there is any key {creden} before trying to access a deeper key.

no autovivification is another possibility.

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}

This is the JSON response, i suppose to capture below for all 1000 users

  "creden": {
        "uName": "5xxxxxxx"
    },
[download]

Obviously not always...

edit

see Basic debugging checklist Point 4 about dumping

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}