Just use the product of a doubled negation to get clear booleans!¹

Perl's definition of false covers different data types and context cases.

from perldata

       A scalar value is interpreted as TRUE in the Boolean sense if i
+t is not
       the null string or the number 0 (or its string equivalent, "0")
+.  The
       Boolean context is just a special kind of scalar context where 
+no
       conversion to a string or a number is ever performed.
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(Null string here means either empty string "" or undef)

from perlsyn

Truth and Falsehood
 
       The number 0, the strings '0' and '', the empty list "()", and 
+"undef"
       are all false in a boolean context. All other values are true.
       Negation of a true value by "!" or "not" returns a special fals
+e value.
       When evaluated as a string it is treated as '', but as a number
+, it is
       treated as 0.
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¹) in this case  my @cell_contents = map { !!$_ } @$array_ref[3..10];

for me the most readable alternative!