Concurrency introduces a high degree of combinatory which may be the source of subtle mistakes. We present a new tool, Quasar, which is based on ASIS and which uses fully the concept of patterns. The analysis of a concurrent Ada program by our tool proceeds in four steps: automatic extraction of the concurrent part of the program; translation of the simplified program into a formal model using predefined patterns that are combined by substitution and merging constructors; analysis of the model both by structural techniques and model-checking techniques; reporting deadlock or starvation results. We demonstrate the usefulness of Quasar by analyzing several variations of a non trivial concurrent program.