Perl:直到条件从未评估为真

Question

我是一个Perl新手,试图找出为什么我的直到条件永远不会在一个基本的猜数游戏中评估为真.

#!/usr/bin/perl
# Ex 10-1

use warnings;

$num = int(1 + rand 100);
print "\$num is $num\n";                # Debug

print "I'm thinking of a number between 1 and 100. What number is it?\n";
until (chomp($guess = <STDIN>) == $num) {
    print "\$guess is $guess\n";        # Debug
    if ($guess =~ /\A\s*(quit|exit)?\s*\z/) {
        print "Exiting.\n";
        exit 0;
    } elsif ($guess =~ /\D/) {
        print "Invalid input. ";
    } else {
        ($guess < $num) ? (print ("Too low. ")) : (print ("Too high. "));
    }
    print ("Guess again.\n");
}
print ("Congrats! You guessed the number.\n");
exit 0;

这是执行的一个例子:

$ ./ex1
$num is 4
I'm thinking of a number between 1 and 100. What number is it?
5
$guess is 5
Too high. Guess again.
3
$guess is 3
Too low. Guess again.
4
$guess is 4
Too high. Guess again.

将$ guess与$ num进行比较,当输入4时,$ guess等于$ num,满足测试条件.然而它仍然进入循环并使其达到打印"太高"的最终(默认)结果.

我也尝试在chomp($ guess =)周围添加另一组括号,但没有帮助.

为什么会这样？

Answer 1

chomp返回删除的字符数,而不是在chomp-ing 之后的修改后的参数,因此您不应该在循环条件中使用返回值.

chomp(my $guess = <STDIN>);

until ($guess == $num) {
    ...
    chomp($guess = <STDIN>);
}