Perl:在这种特殊情况下，哈希不允许使用字母数字键

Question

我通过创建哈希发现了一个奇怪的行为:

perl -e "%x = (1 => 10, p2 => 20); while ( ($k,$v) = each %x ) { print \"key $k value $v\n\";}"

给出以下输出:

key p2 value 20
key 1 value 10

但是，如果我将 key p2 更改为 1p2，则会出现错误:

perl -e "%x = (1 => 10, 1p2 => 20); while ( ($k,$v) = each %x ) { print \"key $k value $v\n\";}"

输出是:

syntax error at -e line 1, near "1p2"
Execution of -e aborted due to compilation errors.

为什么会报错？
(Win10，草莓Perl v5.30.0)

Answer 1

引用 perlop (强调):

The "=>" operator (sometimes pronounced "fat comma") is a synonym for the comma except that it causes a word on its left to be interpreted as a string if it begins with a letter or underscore and is composed only of letters, digits and underscores. This includes operands that might otherwise be interpreted as operators, constants, single number v-strings or function calls. If in doubt about this behavior, the left operand can be quoted explicitly.

由于 1p2 以数字开头，因此 => 的特殊行为不适用。您必须像普通字符串一样引用它以防止解析错误。