I'd say Gauche or Kawa.
Gauche is excellent for system programming but obscured by Guile. Kawa running on the JVM and being ENTERPRISE QUALITY is looked down upon.
Gauche is indeed very solid as a glue language for daily plumbing tasks. As for Kawa, one thing I particularly like about it is that it has high-level units of quantities: https://www.gnu.org/software/kawa/Quantities.html