The easiest way to avoid the warning is to remove the space between print and (.

splain explains the warning in this way:

(W syntax) You've run afoul of the rule that says that any list operator followed by parentheses turns into a function, with all the list operators arguments found inside the parentheses. See "Terms and List Operators (Leftward)" in perlop.

Updated:The warning would be useful if you closed the outer parentheses earlier:

print ((sort { $b <=> $a } grep defined, @_)[0]), " - was a max define
+d value\n";
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The common solution is not to use another parentheses, but to insert a +:

print +(sort { $b <=> $a } grep defined, @_)[0], " - was a max defined
+ value\n";
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