reg --display='payee =~ /February/' books
<<<
2008/01/01 January
    Expenses:Books          $10.00
    Assets:Cash

2008/01/01 End of January
    Expenses:Books          $10.00
    Assets:Cash

2008/01/01 January
    Expenses:Books          $10.00
    Assets:Cash

2008/01/01 End of January
    Expenses:Books          $10.00
    Assets:Cash

2008/01/01 January
    Expenses:Books          $10.00
    Assets:Cash

2008/01/01 End of January
    Expenses:Books          $10.00
    Assets:Cash

2008/02/01 February
    Expenses:Books          $20.00
    Assets:Cash

2008/02/01 End of February
    Expenses:Books          $20.00
    Assets:Cash

2008/02/01 February
    Expenses:Books          $20.00
    Assets:Cash

2008/02/01 End of February
    Expenses:Books          $20.00
    Assets:Cash

2008/02/01 February
    Expenses:Books          $20.00
    Assets:Cash

2008/02/01 End of February
    Expenses:Books          $20.00
    Assets:Cash

>>>1
08-Feb-01 February              Expenses:Books               $20.00       $80.00
08-Feb-01 End of February       Expenses:Books               $20.00      $100.00
08-Feb-01 February              Expenses:Books               $20.00      $120.00
08-Feb-01 End of February       Expenses:Books               $20.00      $140.00
08-Feb-01 February              Expenses:Books               $20.00      $160.00
08-Feb-01 End of February       Expenses:Books               $20.00      $180.00
>>>2
=== 0