I need to insert values of string variables placed in double quotes. I am using below code :-

```
$username="abc";
$password="123";
my $post_data = '{ "auth": {"tenantName":"admin", "passwordCredentials": {"username":"$username","password":"$password"} }}';
print $post_data;

```

It is showing output like :-

```
{ "auth": {"tenantName":"admin", "passwordCredentials": {"username":"$username","password":"$password"} }}

```

But i want output like :-

```
{ "auth": {"tenantName":"admin", "passwordCredentials": {"username":"abc","password":"123}"}}

```