在perl中检测声明的包变量

# package main;
our $f;
sub f{}
sub g {}
1;

我尽我所能,甚至试图询问eval StriNG是否已经通过我们或我的声明$main :: f. (这需要重复,关闭,以及稍后恢复STDERR以减少干扰.)一旦你更改了包,那些临时转回的声明就不再可见了.

下面的技术将检测是否已通过声明$f

use vars qw/ $f /;

代码如下：

package Mymodule;

use warnings;
use Strict;

# using $f will confuse the compiler,generaTing
# warnings of 'Variable "%f" is not available'
# although we're going for $main::f
my $__f = "from Mymodule";

my %IMPORT_OK = (
  '$f' => [f => \$__f],);

sub import {
  my($pkg,@imports) = @_;
  my $callpkg = caller;

  die "I don't speak your dirty Pig-LaTin"
    if $callpkg !~ /\A\w+(::\w+)*\z/ ||
       grep !/\A[\$@%]\w+\z/,@imports;

  foreach my $name (@imports) {
    my($sym,$ref) = @{ $IMPORT_OK{$namE} || [] };
    die "unknown import: $name" unless $sym;

    open my $saverr,">&",\*STDERR or die "dup STDERR: $!";
    close STDERR;

    my $declared = eval qq{
      package $callpkg;
      my(undef)=$name;
      1;
    };

    open STDERR,$saverr or print "restore STDERR: $!";
    die "${Callpkg}::$sym already exists" if $declared;

    {
      no Strict 'refs';
      *{$callpkg . "::" . $sym} = $ref;
    }
  }
}

1;