https://github.com/ingydotnet/git-hub/commit/b9f723cabbbc9fd0444d4cf8653750fd4db1a1fb#commitcomment-15235548

Author: ingydotnet

ext/bashplus/lib/bash+.bash

@@ -75,7 +75,7 @@ bash+:die() {
   [[ $msg =~ $trailing_newline_re ]] && exit 1
 
   local c=($(caller ${DIE_STACK_LEVEL:-${2:-0}}))
-  [[ ${#c[@]} -eq 2 ]] &&
+  (( ${#c[@]} == 2 )) &&
     msg=" at line %d of %s" ||
     msg=" at line %d in %s of %s"
   printf "$msg\n" ${c[@]} >&2