Hello,
These two looks similar to me, but they behave different: 
perl -le '@_ = qw( a b c ); print( ( shift @_ )[ 0, 0 ] );'

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OUTPUT: aa 
perl -le '@_ = qw( a b c ); @A = ( shift @_ )[ 0, 0 ]; print @A'

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OUTPUT: a
Seems like a bug?
My overcome was trivial: 
perl -le '@_ = qw( a b c ); @A = ( shift @_ ) x 2; print @A'

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Update. This behaviour spans some versions, as shown by stevieb in his testing: Re^4: Case where '( shift @_ )[ 0, 0 ]' returns only one value?.
Behaviour (bug) fixed between 5.18 and 5.20, more details --> https://rt.perl.org/Public/Bug/Display.html?id=133769#txn-1606556

In reply to Case where '( shift @_ )[ 0, 0 ]' returns only one value? by rsFalse

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