Perl 是否执行出现在 return 之后的代码？功能？

Question

我有一个丑陋的 Perl 子例程，它有一个嵌套的 if 语句，returns 根据条件不同的值。这很丑陋，因为我不喜欢嵌套的 if 语句。它们很难遵循，所以我想将它分解成单独的 if 语句，但我不确定它是否会改变子例程的执行方式。原始子程序如下：

 sub TacacsInstalled(){

    my $Installed;
    my $InstalledVersion;
    my $InstalledRelease;
    my $NewVersion;
    my $NewRelease;

    $Installed = `rpm -qa | grep tac_plus | wc -l`;
    chomp $Installed;

    # Check to see if Tacacs is installed.
    if ($Installed == 0){ # Tacacs is not installed. Fresh install.
        return "False";
    } else { # Tacacs is installed.  Is it an old version?
        $InstalledVersion = `rpm -q tac_plus --queryformat \"%{VERSION}\""`;
        chomp $InstalledVersion;
        $NewVersion = `rpm -qp ./tac_plus*.x86_64.rpm --queryformat \"%{VERSION}\""`;
        chomp $NewVersion;

        if ($InstalledVersion < $NewVersion) { # Current installed version is too old, must update.
            return "False";
        } else { # Maybe the release is newer.
            $InstalledRelease = `rpm -q tac_plus --queryformat \"%{RELEASE}\""`;
            chomp $InstalledRelease;
            $NewRelease = `rpm -qp ./tac_plus*.x86_64.rpm --queryformat \"%{RELEASE}\""`;
            chomp $NewRelease;

            if ($InstalledRelease < $NewRelease) { # Current installed release is too old, must update.
                return "False";

            } else { # Installed release is newer than or equal to what we're trying to install. Do nothing.
                return "True";
            }
        }
    }
}

我可以改用以下代码来改进此代码吗？

sub TacacsInstalled(){

    my $Installed;
    my $InstalledVersion;
    my $InstalledRelease;
    my $NewVersion;
    my $NewRelease;

    $Installed = `rpm -qa | grep tac_plus | wc -l`;
    chomp $Installed;

    # Check to see if Tacacs is installed.
    if ($Installed == 0){ return "False" }; # Tacacs is not installed perform a fresh install.

    # If we got this far then Tacacs must be installed.  Is it an old version?
    $InstalledVersion = `rpm -q tac_plus --queryformat \"%{VERSION}\""`;
    chomp $InstalledVersion;
    $NewVersion = `rpm -qp ./tac_plus*.x86_64.rpm --queryformat \"%{VERSION}\""`;
    chomp $NewVersion;      

    if ($InstalledVersion < $NewVersion) { return "False" }; # Current installed version is too old, must update.

    # The Version is the same so then is the release is newer?
    $InstalledRelease = `rpm -q tac_plus --queryformat \"%{RELEASE}\""`;
    chomp $InstalledRelease;
    $NewRelease = `rpm -qp ./tac_plus*.x86_64.rpm --queryformat \"%{RELEASE}\""`;
    chomp $NewRelease;

    if ($InstalledRelease < $NewRelease) { return "False" }; # Current installed release is too old, must update.

    # Installed release is newer than or equal to what we're trying to install. Do nothing.
    return "True";

}

Answer 1

不，Perl 不会在 return 之后执行代码。这就是 return!

的重点

Answer 2

不要在 Perl 子程序中使用原型。只有 sub TacacsInstalled { ... } 是正确的
使用 snake_case 优先于 CamelCase 标识符
将所有变量声明为尽可能晚，永远不要在代码顶部的块中声明
正确使用Perl的语句修饰符
None 您的反引号字符串看起来是正确的：每个字符串的末尾都有一个备用双引号。双引号不需要在反引号字符串中转义

我还想说，返回 Perl true 或 false 值（0、'0' 和undef 为假；其他均为真）优于返回 True 和 False 字符串

我会写这个

sub tacacs_installed {

    my $installed = `rpm -qa | grep tac_plus | wc -l`;
    chomp $installed;

    return 'False' if $installed == 0;    # Tacacs is not installed. Fresh install.

    my $installed_version = `rpm -q tac_plus --queryformat \"%{VERSION}\""`;
    chomp $installed_version;

    my $new_version = `rpm -qp ./tac_plus*.x86_64.rpm --queryformat \"%{VERSION}\""`;
    chomp $new_version;

    return 'False' if $installed_version < $new_version;  # Current installed version is too old, must update.

    my $installed_release = `rpm -q tac_plus --queryformat \"%{RELEASE}\""`;
    chomp $installed_release;

    my $new_release = `rpm -qp ./tac_plus*.x86_64.rpm --queryformat \"%{RELEASE}\""`;
    chomp $new_release;

    return 'False' if $installed_release < $new_release;  # Current installed release is too old, must update.

    return 'True';
}

Perl 是否执行出现在 return 之后的代码？功能？

Does Perl execute code that appears after the return; function?

perl

scripting

subroutine