By default, GHCi don't allow multi line expressions. For example, you should type the expression `1+2*3` in same line.
Prelude> 1+
<interactive>:9:3:
parse error (possibly incorrect indentation or mismatched brackets)
To span an expression across multiple lines, you need to use multiline block. You should type :{ to start a multi line block, and type :} to end multi line block.
Prelude> :{
Prelude| 1+
Prelude| 2
Prelude| *
Prelude| 3
Prelude| :}
7
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