\ [
    [0] {
        error     undef,
        parser    "Spreadsheet::XLSX",
        sheet     {
            Sheet1   1
        },
        sheets    1,
        type      "xlsx",
        version   0.13
    },
    [1] {
        attr     [],
        B1       "Income Statement 2014",
        B2       "Revenue",
        B3       "Cost of goods sold",
        B4       "Gross profit",
        B5       "Financing costs",
        B6       "Tax",
        B7       "Net profit",
        cell     [
            [0] [],
            [1] [],
            [2] [
                [0] undef,
                [1] "Income Statement 2014",
                [2] "Revenue",
                [3] "Cost of goods sold",
                [4] "Gross profit",
                [5] "Financing costs",
                [6] "Tax",
                [7] "Net profit"
            ],
            [3] [
                [0] undef,
                [1] undef,
                [2] 50000,
                [3] 2500,
                [4] 47500,
                [5] 7150,
                [6] 10087.5,
                [7] 30262.5
            ]
        ],
        C2       " $ 50,000.00 ",
        C3       " $ 2,500.00 ",
        C4       " $ 47,500.00 ",
        C5       " $ 7,150.00 ",
        C6       " $ 10,087.50 ",
        C7       " $ 30,262.50 ",
        label    "Sheet1",
        maxcol   3,
        maxrow   7
    }
]
This shows that $workbook is an arrayref, whose first element describes the file, and subsequent elements represent the individual worksheets. The label key pair contains the worksheet name, access it like this:

$workbook->[1]{label}; #Sheet1