use JSON qw(decode_json);

my $jsonString = '{
    "_id" : "ObjectId(52dfd2750cf2169251fe8d3c)",
    "closed_on": "ISODate(2014-01-30T18:30:00Z)",
    "companies": [
        {
            "_id": "ObjectId(52dfd2750cf2169251fe8d3f)",
            "comp_name": "Test1"
        },
        {
            "_id": "ObjectId(52dfd7950cf2169251fe8d47)",
            "comp_name": "Test2"
        }
    ],
    "contacts" : [
        {
            "_id": "ObjectId(52dfd2750cf2169251fe8d3e)",
            "fname": "Solve",
            "lname": "Scottt",
            "email": "email1@gmail.com",
            "company": "Test111"
        },
        {
            "_id": "ObjectId(52dfd7950cf2169251fe8d46)",
            "fname": "signe",
            "lname": "towne",
            "email": "email2@gmail.com",
            "company": "Test222"
        }
    ],
    "crt_by": "creator@gmail.com",
    "currency": "USD",
    "type": "None"
}';

my $decodedJSON = decode_json($jsonString);
print "crts_by = $decodedJSON->{'crt_by'}\n";
print "Contact 1 => fname = $decodedJSON->{'contacts'}[0]{'fname'}, company = $decodedJSON->{'contacts'}[0]{'company'}\n";