What is wrong with this statement?

Questions
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1

X=“abcd”

Y=“dfec”

both statement have been echoed. But Why does the first assignment of X not assigned? Only the second assignment Y is assigned?

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2

I just imported it using Import["/tmp/ASM918.txt", "FASTA"] and that seemed to work fine. In case it makes a difference, I am using the version of mathematica currently under development (I’d be surprised if this was a bug in prior versions though).