The variable rule program is one of the predominant data analysis tools used in sociolinguistics, employed successfully for over three decades to quantitatively assess the influence of multiple factors on linguistic variables. However, its most popular current version, GoldVarb, lacks flexibility and also isolates its users from the wider community of quantitative linguists. A new version of the variable rule program, Rbrul, attempts to resolve these concerns, and with mixed-effects modelling also addresses a more serious problem whereby GoldVarb overestimates the significance of effects. Rbrul's superior performance is demonstrated on both simulated and real data sets.