After fixing the unclosed string literal, I get output. Is there another problem?

a 2 2
b 5 5
c 10 10
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a 1 1
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a 1 1
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a 1 1
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a 1 1
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a 1 1
b 1 1
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a 1 1
b 1 1
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a 1 1
b 1 1
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a 1 1
b 1 1
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b 1 1
d 10 10
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gives

c : 10: 10
a : 10: 10
b : 10: 10
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By the way, are you sure you want if (exists $a[$j]{$key})? Notice the lack of "d" in the output.