Perl中嵌套的'if‘或其他内容

if (condition1) {
    # 执行一些代码
    if (condition2) {
        # 如果condition1和condition2都为真，则执行这里的代码
    }
}

if (condition1) {
    # 执行一些代码
} elsif (condition2) {
    # 如果condition1为假而condition2为真，则执行这里的代码
} else {
    # 如果所有条件都为假，则执行这里的代码
}

sub check_user_access {
    my ($user_level, $resource) = @_;

    if ($user_level >= 1) {
        if ($resource eq 'public') {
            return "Access granted to public resource.";
        } elsif ($resource eq 'private') {
            if ($user_level >= 2) {
                return "Access granted to private resource.";
            } else {
                return "Access denied to private resource.";
            }
        }
    }

    return "Access denied.";
}

print check_user_access(2, 'private'); # 输出: Access granted to private resource.