From https://docs.epics-controls.org/en/latest/appdevguide/databaseDefinition.html#macro-substitution

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Example 1
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$(name)

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(macro_expansion (variable))

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Example 2
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${name}

---

(macro_expansion (variable))

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Example 3
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$(name_$(sel))

---

(macro_expansion
 (variable (macro_expansion (variable))))

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Example 4
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$(name=default)

---

(macro_expansion
 (variable)
 (string))

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Example 5
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$(abcd=$(a)$(b)$(c)$(d),a=A,b=B,c=C,d=D)

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(macro_expansion
 (variable)
 (string
  (macro_expansion (variable))
  (macro_expansion (variable))
  (macro_expansion (variable))
  (macro_expansion (variable)))
 (override (variable) (string))
 (override (variable) (string))
 (override (variable) (string))
 (override (variable) (string)))
