The European Southern Observatory (ESO) provides pipelines to reduce data for almost all Very Large Telescopes (VLT) instruments. In order to reduce the cost of development, verification, and maintenance of ESO pipelines, and at the same time to improve the scientific quality of pipeline data products, ESO has developed a limited set of versatile and instrument-independent high-level scientific functions to be used in the pipelines. These routines are provided by the High-level Data Reduction Library (HDRL). HDRL is already used by more than half of the ESO public pipelines with clear benefits on implementation and improved quality of the final data products. HDRL is also used in the core functions of the ESO Toolkit Pipeline (esotk). The latter includes a few recipes to perform stacking of 1D spectra and the detection and correction of fringes on images. This poster describes design choices, summarises our experiences implementing HDRL modules and using them in the pipelines, and provides an overview of the different functionality. Finally, we will focus on a number of recent HDRL improvements.