Pirl was recently listed on BTC-Alpha exchange with a direct pair to USD.
In order to buy Pirl with USD you need to deposit funds in your account.
Currently the lowest fee method for depositing USD is Perfect Money.
You can create an account here: https://perfectmoney.is/signup.html
When you have created and credited your Perfect Money account, you can deposit USD in BTC-Alpha:
Step 1: Sign in to your Personal Cabinet, enter your username and password
Step 2: You should fill up your merchant account with cryptocurrency / currency that you are interested in. To do this, tap the “Finance” button in the dialog box under your e-mail address at the top-right corner:
Step 3: It will bring you to the «My wallets» section. Select the appropriate currency and click the “Deposit” button.
Step 4: Select one of the systems provided in the BTC-Alpha Exchange Market (sign up beforehand) in order to deposit funds into your private account in the exchange market.
Take the USD as an example:
Select: Perfect, enter the amount you would like to deposit and click Next. This window will pop-up:
Step 5: Now you can purchase Pirl by selecting PIRL/USD market and placing your buy order