在完全一般的情况下,由于perlref的以下摘录,您无法做您想做的事情:
*foo{THING}
undef
如果该特定 THING 尚未使用,则返回,标量除外。如果尚未使用,*foo{SCALAR}
则返回对匿名标量的引用。$foo
这可能会在未来的版本中改变。
但是,如果您愿意接受任何标量必须具有定义的值才能被检测到的限制,那么您可以使用诸如
#! /usr/bin/perl
use strict;
use warnings;
open my $fh, "<", \$_; # get DynaLoader out of the way
my %before = %main::;
require "my.config";
my %after = %main::;
foreach my $name (sort keys %after) {
unless (exists $before{$name}) {
no strict 'refs';
my $glob = $after{$name};
print "\$$name\n" if defined ${ *{$glob}{SCALAR} };
print "\@$name\n" if defined *{$glob}{ARRAY};
print "%$name\n" if defined *{$glob}{HASH};
print "&$name\n" if defined *{$glob}{CODE};
print "$name (format)\n" if defined *{$glob}{FORMAT};
print "$name (filehandle)\n" if defined *{$glob}{IO};
}
}
会带你到那里。
与my.config
_
$JACKPOT = 3_756_788;
$YOU_CANT_SEE_ME = undef;
@OPTIONS = qw/ apple cherries bar orange lemon /;
%CREDITS = (1 => 1, 5 => 6, 10 => 15);
sub is_jackpot {
local $" = ""; # " fix Stack Overflow highlighting
"@_[0,1,2]" eq "barbarbar";
}
open FH, "<", \$JACKPOT;
format WinMessage =
You win!
.
输出是
%学分
FH(文件句柄)
$头奖
@选项
WinMessage(格式)
&is_jackpot
打印名称需要一些工作,但我们可以使用Data::Dumper
模块来承担部分负担。前面的事情类似:
#! /usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
sub _dump {
my($ref) = @_;
local $Data::Dumper::Indent = 0;
local $Data::Dumper::Terse = 1;
scalar Dumper $ref;
}
open my $fh, "<", \$_; # get DynaLoader out of the way
my %before = %main::;
require "my.config";
my %after = %main::;
我们需要稍微不同地转储各种插槽,并在每种情况下删除引用的陷阱:
my %dump = (
SCALAR => sub {
my($ref,$name) = @_;
return unless defined $$ref;
"\$$name = " . substr _dump($ref), 1;
},
ARRAY => sub {
my($ref,$name) = @_;
return unless defined $ref;
for ("\@$name = " . _dump $ref) {
s/= \[/= (/;
s/\]$/)/;
return $_;
}
},
HASH => sub {
my($ref,$name) = @_;
return unless defined $ref;
for ("%$name = " . _dump $ref) {
s/= \{/= (/;
s/\}$/)/;
return $_;
}
},
);
最后,我们遍历 和 之间的集合%before
差%after
:
foreach my $name (sort keys %after) {
unless (exists $before{$name}) {
no strict 'refs';
my $glob = $after{$name};
foreach my $slot (keys %dump) {
my $var = $dump{$slot}(*{$glob}{$slot},$name);
print $var, "\n" if defined $var;
}
}
}
使用my.config
你的问题,输出是
$ ./prog.pl
@A = ('a','b','c')
%B = ('b' => '蜜蜂')
$C = '看'