带有goto语句和if else条件的问题

Question

我正在尝试创建一个简单的perl赋值，用于相等检查和goto标签概念。

用户输入数字，发生相等性检查，询问用户是否要检查更多，如果是，则重复，否则退出。为此使用"goto“

发出- y/n检查重复，y表示重复标签。即使我输入"n“，它也会一直转到标签循环。为什么包含"goto“的"if”条件没有得到满足？下面的代码

#Checking Equality

Loop: print "\Checking Equality\n";
print "Enter number for variable a\n";
$a = <stdin>;
print "Enter number for variable b\n";
$b = <stdin>;
if ( $a == $b ) {
    print 'a and b are equal';
    print "\n\n";
}
else {
    print 'a and b are not equal';
}
print "\n\n";
print "do you want to check more? Enter y/n\n";
$c = <stdin>;
if ( $c == "y" ) {
    goto Loop;
}
elsif ( $c == "n" ) {
    print "Exiting\n";
}

输出-

Checking Equality
Enter number for variable a
3
Enter number for variable b
4
a and b are not equal

do you want to check more? Enter y/n
n         
Checking Equality   #### despite of entering n goto Loop is getting executed
Enter number for variable a

Answer 1

只需使用chomp函数删除换行符，并对字符串使用eq比较。

use strict;
use warnings;

Loop: print "\nChecking Equality\n";
print "Enter number for variable a\n";
my $a = <stdin>;
print "Enter number for variable b\n";
my $b = <stdin>;
if ( $a == $b ) {
    print 'a and b are equal';
    print "\n\n";
}
else {
    print 'a and b are not equal';
}
print "\n\n";
print "do you want to check more? Enter y/n\n";

chomp(my $c = <stdin>);

if ( $c eq "y" ) {
    goto Loop;
}
else {
    print "Exiting\n";
}

Answer 2

您选择了非最佳方法来使用goto的标签。

相反，循环更适合执行用户输入。用户停留在循环中，直到他/她不指定他/她准备离开。

用户的输入在用于比较之前也应该去掉换行符\n。

由于用户假设要多次提供输入，因此使用较小的子程序来打印“输入提示”、收集输入、剥离换行符并返回输入值将是有益的。通过这样做，程序变得更短，更容易阅读。

使用eq执行字符串比较操作，使用==执行数字比较。

use strict;
use warnings;
use feature 'say';

my $answer = 'y';

while( $answer eq 'y' ) {
    my $num_1 = get_input('Enter variable num_1: ');
    my $num_2 = get_input('Enter variable num_2: ');

    my $compare = $num_1 == $num_2 ? 'EQUIAL' : 'NOT EQUIAL';

    say "\nNumbers are $compare\n";

    $answer = get_input('Would you like to continue? (y/n) ');
    $answer = lc $answer;
    say '-' x 35;
}

sub get_input {
    my $msg = shift;
    my $input;

    print $msg;
    $input = <>;
    chomp $input;

    return $input;
}