-# b4_percent_define_get(VARIABLE)
-# -------------------------------
-# Mimic muscle_percent_define_get in ../src/muscle-tab.h exactly. That is, if
-# the %define variable VARIABLE is defined, emit its value. Also, record
+# b4_percent_define_get(VARIABLE, [DEFAULT])
+# ------------------------------------------
+# Mimic muscle_percent_define_get in ../src/muscle-tab.h. That is, if
+# the %define variable VARIABLE is defined, emit its value. Contrary
+# to its C counterpart, return DEFAULT otherwise. Also, record