Perl's bad at arithmetic?

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print +( 1<<(2**$_+$_-1) )-1 for 4,5,6;;
524287
...
1111111111111111111000000000000000000000000000000000000000000000
1111111111111111111111111111111111110000000000000000000000000000
1111100000000000000000000000000000000000000000000000000000000000

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1111111111111111111000000000000000000000000000000000000000000000

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1111111111111111111111111111111111110000000000000000000000000000

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1111111111111111111111111111111111111111111111111111111111111111

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