When a constant is assigned the value of a built-in function as the first statement of a program, it can cause the interpreted front end to crash. I think that a translated front end does not because it ends up accessing valid memory, but part of the sequence structure, not the sequence data, masking the error.
In other places, this might also lead to incorrect behavior:
constant cmds = command_line()
The parser checks to make sure the last op was an ASSIGN before looking to see if it was a literal.
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