In workon.sh, the PS1 is updated the new virtual environment. If workon.sh is executed multiple times (e.g. when switching between environments), the old environment is kept in this variable, creating large string of virtual envs like this:

(faasm-exp) (faasm-exp) (faasm) (faasm-exp) (faasm) mmathys@koala9:~/experiment-base$

An easy fix could be to change this line to

export PS1="(faasm)"