how to have multiple replace statements when using String manipulation

Hi there,

I am trying to replace the multiple strings in Column1 with different names.

Column1

a

b

c

d

My expression in String manipulation node is:

replace($Column1$, “a”, “aa”);

replace($Column1$, “b”, “bb”)

I am getting this error message:

Invalid settings:

org.knime.ext.sun.nodes.script.compile.CompilationFailedException:Unable to compile expression

Unreachable coe.