If you call this with argument "unused=true" it searches for the translation strings that exist in en_US but are never used.
IMPORTANT: that can take quite a lot of time (up to 10 minutes), you need to tune the max_execution_time on your php.ini accordingly.

Duplicate strings in lang files in /home/schutz/www/dolibarr/dev/translation/../../htdocs/langs/en_US/ - 54 found

#StringFile and lines
3IdModuleadmin.lang (136 - Module ID)
modulebuilder.lang (2 - Module id)
4NoticePeriodadmin.lang (288 - Notice period)
holiday.lang (123 - Notice period)
5LanguageFileadmin.lang (396 - Language file)
modulebuilder.lang (57 - File for language)
6PriceFormatInCurrentLanguageadmin.lang (439 - Price Format In Current Language)
companies.lang (33 - Price display format in the current language and currency)
7Upgradeadmin.lang (1187 - Upgrade)
install.lang (100 - Upgrade)
8Serveradmin.lang (1198 - Server)
install.lang (46 - Server)
9DatabaseServeradmin.lang (1200 - Database host)
install.lang (49 - Database server)
10DatabaseNameadmin.lang (1201 - Database name)
install.lang (50 - Database name)
11DriverTypeadmin.lang (1209 - Driver type)
install.lang (45 - Driver type)
12Buyadmin.lang (1866 - Buy)
products.lang (56 - Purchase)
13Selladmin.lang (1867 - Sell)
products.lang (55 - Sell)
14AccountancyCodeadmin.lang (1870 - Accounting Code)
companies.lang (299 - Accounting account)
15CashDeskadmin.lang (1899 - Point of Sale)
cashdesk.lang (3 - Point of sale)
16ByDefaultInListadmin.lang (2075 - Show by default on list view)
categories.lang (97 - By default in list)
1LineIdaccountancy.lang (143 - Id line)
exports.lang (44 - Id of line)
2CustomerInvoicePaymentaccountancy.lang (242 - Payment of invoice customer)
banks.lang (108 - Customer payment)
17AffectedToagenda.lang (10 - Assigned to)
projects.lang (124 - Allocated to)
18Locationagenda.lang (14 - Location)
stocks.lang (40 - Location)
19ReceptionClassifyClosedInDolibarragenda.lang (69 - Reception %s classified closed)
receptions.lang (51 - Reception %s classified Closed)
20InterventionSentByEMailagenda.lang (87 - Intervention %s sent by email)
interventions.lang (39 - Intervention %s sent by email)
21DeleteTypeassets.lang (20 - Delete)
members.lang (99 - Delete)
22ShowTypeCardassets.lang (23 - Show model '%s')
members.lang (169 - Show type '%s')
23IBANbanks.lang (33 - IBAN number)
bills.lang (495 - IBAN)
24BICbanks.lang (34 - BIC/SWIFT code)
bills.lang (498 - BIC/SWIFT)
25SubscriptionPaymentbanks.lang (110 - Subscription payment)
members.lang (183 - Contribution payment)
26InvoiceRefbills.lang (364 - Invoice ref.)
receiptprinter.lang (72 - Invoice ref)
27Salariesbills.lang (663 - Salaries)
salaries.lang (7 - Salaries)
28NoSupplierOrderboxes.lang (84 - No recorded purchase order)
orders.lang (87 - No purchase order)
29ShowCompanycashdesk.lang (32 - Show company)
companies.lang (315 - Third Party)
30Historycashdesk.lang (74 - History)
suppliers.lang (8 - History)
31DeleteFromCatcategories.lang (87 - Remove from tags/category)
compta.lang (281 - Remove from accounting group)
32Customercommercial.lang (4 - Customer)
companies.lang (253 - Customer)
33Prospectcommercial.lang (6 - Prospect)
companies.lang (251 - Prospect)
propal.lang (12 - Prospect)
34ShowTaskcommercial.lang (19 - Show task)
projects.lang (41 - Show task)
35ContractStatusClosedcontracts.lang (9 - Closed)
products.lang (88 - Closed)
36MinimumAmountdonations.lang (27 - Minimum amount is %s)
members.lang (214 - Minimum amount of membership payment (has priority on any default amounts))
37NewSubscriptioneventorganization.lang (121 - Registration)
members.lang (79 - New contribution)
38ExportsAreaexports.lang (2 - Exports)
other.lang (290 - Exports area)
39ExportableDatasexports.lang (6 - Exportable dataset)
other.lang (294 - Exportable data)
40AvailableFormatsexports.lang (28 - Available Formats)
other.lang (291 - Available formats)
41ChooseFileToImportexports.lang (67 - Upload file then click on the %s icon to select file as source import file...)
stocks.lang (255 - Upload file then click on the %s icon to select file as source import file...)
42CreateUserinstall.lang (56 - Create user account or grant user account permission on the Dolibarr database)
users.lang (31 - Create user)
43CreatedByother.lang (126 - Created by %s)
ticket.lang (161 - Created by)
44Stockproducts.lang (51 - Stock)
stocks.lang (18 - Stock)
45Stocksproducts.lang (53 - Stocks and location (warehouse) of products)
stocks.lang (19 - Stocks)
46Movementsproducts.lang (54 - Movements)
stocks.lang (28 - Movements)
47Suppliersproducts.lang (93 - Vendors)
suppliers.lang (2 - Vendors)
48ListOfStockMovementsproducts.lang (100 - List of stock movements)
stocks.lang (31 - List of stock movements)
49Unitproducts.lang (183 - Unit)
stocks.lang (47 - Unit)
50ContractSignedpropal.lang (95 - Contract signed)
recruitment.lang (48 - Contract signed)
51BankTransferAmountsalaries.lang (32 - Amount of credit transfer)
withdrawals.lang (122 - Amount of Credit Transfer request:)
52WithdrawalReceiptsalaries.lang (33 - Credit transfer order)
withdrawals.lang (12 - Direct debit order)
53OrderWaitingsalaries.lang (34 - Pending order)
withdrawals.lang (94 - Waiting for treatment)
54NewUserticket.lang (296 - New user)
users.lang (30 - New user)