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/ykard/www/draky_net/dolibarr/dev/translation/../../htdocs/langs/en_US/ - 53 found

#StringFile and lines
27InvoiceSubtypebills.lang (671 - Invoice Subtype)
main.lang (1298 - Invoice subtype)
35AccountancyCodecompanies.lang (300 - Accounting account)
main.lang (894 - Accounting Code)
3IdModuleadmin.lang (136 - Module ID)
modulebuilder.lang (2 - Module id)
4NoticePeriodadmin.lang (288 - Notice period)
holiday.lang (126 - 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 (1191 - Upgrade)
install.lang (101 - Upgrade)
8Serveradmin.lang (1202 - Server)
install.lang (46 - Server)
9DatabaseServeradmin.lang (1204 - Database host)
install.lang (49 - Database server)
10DatabaseNameadmin.lang (1205 - Database name)
install.lang (50 - Database name)
11DriverTypeadmin.lang (1213 - Driver type)
install.lang (45 - Driver type)
12Buyadmin.lang (1872 - Buy)
products.lang (56 - Purchase)
13Selladmin.lang (1873 - Sell)
products.lang (55 - Sell)
14CashDeskadmin.lang (1909 - Point of Sale)
cashdesk.lang (3 - Point of sale)
15ByDefaultInListadmin.lang (2085 - Show by default on list view)
categories.lang (99 - By default in list)
1LineIdaccountancy.lang (145 - Id line)
exports.lang (44 - Id of line)
2CustomerInvoicePaymentaccountancy.lang (251 - Payment of invoice customer)
banks.lang (107 - Customer payment)
16AffectedToagenda.lang (10 - Assigned to)
projects.lang (124 - Allocated to)
17Locationagenda.lang (14 - Location)
stocks.lang (37 - Location)
18ReceptionClassifyClosedInDolibarragenda.lang (70 - Reception %s classified closed)
receptions.lang (50 - Reception %s classified Closed)
19InterventionSentByEMailagenda.lang (88 - Intervention %s sent by email)
interventions.lang (48 - Intervention %s sent by email)
20DeleteTypeassets.lang (20 - Delete)
members.lang (99 - Delete)
21ShowTypeCardassets.lang (23 - Show model '%s')
members.lang (169 - Show type '%s')
22IBANbanks.lang (32 - IBAN number)
bills.lang (498 - IBAN)
23BICbanks.lang (33 - BIC/SWIFT code)
bills.lang (503 - BIC/SWIFT)
24SubscriptionPaymentbanks.lang (109 - Subscription payment)
members.lang (183 - Contribution payment)
25InvoiceRefbills.lang (366 - Invoice ref.)
receiptprinter.lang (72 - Invoice ref)
26Salariesbills.lang (670 - Salaries)
salaries.lang (7 - Salaries)
28NoSupplierOrderboxes.lang (83 - No purchase order recorded)
orders.lang (87 - No purchase order)
29ShowCompanycashdesk.lang (32 - Show company)
companies.lang (316 - Third Party)
30Historycashdesk.lang (74 - History)
suppliers.lang (8 - History)
31DeleteFromCatcategories.lang (88 - Remove from tags/category)
compta.lang (294 - Remove from accounting group)
32Customercommercial.lang (4 - Customer)
companies.lang (254 - Customer)
33Prospectcommercial.lang (6 - Prospect)
companies.lang (252 - Prospect)
propal.lang (12 - Prospect)
34ShowTaskcommercial.lang (19 - Show task)
projects.lang (41 - Show task)
36ContractStatusClosedcontracts.lang (9 - Closed)
products.lang (88 - Closed)
37MinimumAmountdonations.lang (27 - Minimum amount is %s)
members.lang (215 - Minimum amount of membership payment (has priority on any default amounts))
38NewSubscriptioneventorganization.lang (121 - Registration)
members.lang (79 - New contribution)
39ExportsAreaexports.lang (2 - Exports)
other.lang (296 - Exports area)
40ExportableDatasexports.lang (6 - Exportable dataset)
other.lang (300 - Exportable data)
41AvailableFormatsexports.lang (28 - Available Formats)
other.lang (297 - Available formats)
42ChooseFileToImportexports.lang (67 - Upload file then click on the %s icon to select file as source import file...)
stocks.lang (252 - Upload file then click on the %s icon to select file as source import file...)
43CreateUserinstall.lang (56 - Create user account or grant user account permission on the Dolibarr database)
users.lang (31 - Create user)
44CreatedByother.lang (129 - Created by %s)
ticket.lang (169 - Created by)
45Stockproducts.lang (51 - Stock)
stocks.lang (18 - Stock)
46Stocksproducts.lang (53 - Stocks and location (warehouse) of products)
stocks.lang (19 - Stocks)
47Movementsproducts.lang (54 - Movements)
stocks.lang (28 - Movements)
48Suppliersproducts.lang (93 - Vendors)
suppliers.lang (2 - Vendors)
49Unitproducts.lang (182 - Unit)
stocks.lang (44 - Unit)
50ContractSignedpropal.lang (95 - Contract signed)
recruitment.lang (48 - Contract signed)
51WithdrawalReceiptsalaries.lang (32 - Credit transfer order)
withdrawals.lang (12 - Direct debit order)
52OrderWaitingsalaries.lang (33 - Pending order)
withdrawals.lang (94 - Waiting for treatment)
53NewUserticket.lang (305 - New user)
users.lang (30 - New user)