为什么这个程序有效？ 我试图创建一个语法错误

Question

I'm running ActiveState's 32 bit ActivePerl 5.14.2 on Windows 7. I wanted to mess around with a Git pre-commit hook to detect programs being checked in with syntax errors. (Somehow I just managed to do such a bad commit.) So as a test program I randomly jotted this:

use strict;
use warnings;

Syntax error!

exit 0;

However, it compiles and executes with no warnings, and errorlevel is zero on exit. How is this valid syntax?

转载于:https://stackoverflow.com/questions/11695110/why-is-this-program-valid-i-was-trying-to-create-a-syntax-error

Answer 1

Perl has a syntax called "indirect method notation". It allows

Foo->new($bar)

to be written as

new Foo $bar

So that means

Syntax error ! exit 0;

is the same as

error->Syntax(! exit 0);

or

error->Syntax(!exit(0));

Not only is it valid syntax, it doesn't result in a run-time error because the first thing executed is exit(0).