Why do Perl control statements require braces?

Question

This may look like the recent question that asked why Perl doesn't allow one-liners to be "unblocked," but I found the answers to that question unsatisfactory because they either referred to the syntax documentation that says that braces are required, which I think is just begging the question, or ignored the question and simply gave braceless alternatives.

Why does Perl require braces for control statements like if and for? Put another way, why does Perl require blocks rather than statements, like some other popular languages allow?

Answer 1

One reason could be that some styles dictate that you should always use braces with control structures, even for one liners, in order to avoid breaking them later, e.g.:

if (condition)     myObject.doSomething(); else     myObject.doSomethingElse(); 

Then someone adds something more to the first part:

if (condition)    myObject.doSomething();    myObject.doSomethingMore(); // Syntax error next line else     myObject.doSomethingElse(); 

Or worse:

if (condition)    myObject.doSomething(); else     myObject.doSomethingElse();    myObject.doSomethingMore(); // Compiles, but not what you wanted. 

In Perl, these kinds of mistakes are not possible, because not using braces with control structures is always a syntax error. In effect, a style decision has been enforced at the language syntax level.

Whether that is any part of the real reason, only Larry's moustache knows.

Answer 2

One reason could be that some constructs would be ambiguous without braces :

foreach (@l) do_something unless $condition; 

Does unless $condition apply to the whole thing or just the do_something statement?

Of course this could have been worked out with priority rules or something, but it would have been yet another way to create confusing Perl code :-)