全局符号“@str”需要明确的包名

Question

我是新用Perl，我已经面临这个问题：

Global symbol "@str" requires explicit package name (did you forget to declare "my @str"?) at F:\Distrib\LingUtils9\Scripts\CompareLists\CompareLists.pl line 167 

一段代码，导致此消息，可以作为一个PROGRAMM，但不起作用。这是它：

my $containsSub = 0; 
my $str = "This is a string!"; 
my $substr = "string"; 
my $indexOfSub = index($str, $substr); 
if ($indexOfSub != -1) 
{ 
    if (length($substr)==length($str)) 
    { 
      $containsSub = 1; 
    } 
    elsif (($indexOfSub == 0)&&(($str[$indexOfSub + length($substr)]=='?')||($str[$indexOfSub + length($substr)]=='!')||($str[$indexOfSub + length($substr)]=='.')||($str[$indexOfSub + length($substr)]==' ')||($str[$indexOfSub + length($substr)]=='\t'))) 
    { 
      $containsSub = 1; 
    } 
    elsif ((length($str) == $indexOfSub + length($substr))&&(($str[$indexOfSub-1]=='.')||($str[$indexOfSub-1]==' ')||($str[$indexOfSub-1]=='\t')||($str[$indexOfSub-1]=='?')||($str[$indexOfSub-1]=='.')||($str[$indexOfSub-1]=='!'))) 
    { 
      $containsSub = 1; 
    } 
    elsif ((($str[$indexOfSub-1]=='?')||($str[$indexOfSub-1]=='!')||($str[$indexOfSub-1]=='.')||($str[$indexOfSub-1]==' ')||($str[$indexOfSub-1]=='\t'))||(($str[$indexOfSub+length($substr)]=='?')||($str[$indexOfSub+length($substr)]=='!')||($str[$indexOfSub+length($substr)]=='.')||($str[$indexOfSub+length($substr)]==' ')||($str[$indexOfSub+length($substr)]=='\t'))) 
    { 
      $containsSub = 1; 
    } 
} 
print $containsSub; 

这是非常原始的行中的子行内容验证，并且它工作正常。但是，这（只是copypaste）：

sub containsKey 
{ 
    my $containsSub = 0; 
    my $str = "This is a string!"; 
    my $substr = "string"; 
    my $indexOfSub = index($str, $substr); 
    if ($indexOfSub != -1) 
    { 
     if (length($substr)==length($str)) 
     { 
      $containsSub = 1; 
     } 
     elsif (($indexOfSub == 0)&&(($str[$indexOfSub + length($substr)]=='?')||($str[$indexOfSub + length($substr)]=='!')||($str[$indexOfSub + length($substr)]=='.')||($str[$indexOfSub + length($substr)]==' ')||($str[$indexOfSub + length($substr)]=='\t'))) 
     { 
      $containsSub = 1; 
     } 
     elsif ((length($str) == $indexOfSub + length($substr))&&(($str[$indexOfSub-1]=='.')||($str[$indexOfSub-1]==' ')||($str[$indexOfSub-1]=='\t')||($str[$indexOfSub-1]=='?')||($str[$indexOfSub-1]=='.')||($str[$indexOfSub-1]=='!'))) 
     { 
      $containsSub = 1; 
     } 
     elsif ((($str[$indexOfSub-1]=='?')||($str[$indexOfSub-1]=='!')||($str[$indexOfSub-1]=='.')||($str[$indexOfSub-1]==' ')||($str[$indexOfSub-1]=='\t'))||(($str[$indexOfSub+length($substr)]=='?')||($str[$indexOfSub+length($substr)]=='!')||($str[$indexOfSub+length($substr)]=='.')||($str[$indexOfSub+length($substr)]==' ')||($str[$indexOfSub+length($substr)]=='\t'))) 
     { 
      $containsSub = 1; 
     } 
    } 
    return $containsSub; 
} 
my $keyContains = containsKey(); 

print $keyContains; 

使得在命令行

Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
3. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
3. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
3. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
3. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
3. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
7. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
7. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
7. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
7. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
7. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 16 
7. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Global symbol "@str" requires explicit package name (did you forget to declare " 
my @str"?) at \Compare.pl line 17 
1. 
Execution of \Compare.pl aborted 
due to compilation errors. 

这个输出，我只是不明白那是什么。

Answer 1

这是因为perl字符串不是像某些语言中的字符数组。因此$str[3]不是访问$str的有效方式。但是，它会访问@str的第三个元素，该元素不存在并且尚未声明，因此是警告。

如果您希望使用偏移量处理字符串，则需要substr。或my @chars_in_str = split //, $str;

更广泛地说，虽然这看起来像一个相当肮脏的方式来尝试和正则表达式匹配。

我建议你实际上想要做的是：

if ($str =~ m/\b$substr\b/) { 
    $containsSub = 1; 
} 

\b是“字边界” Perl的正则表达式，因此将匹配标点符号或空格的东西，虽然它不是严格的相当于你在做什么（有一大堆更多的标点符号可以工作）。

您还应该注意 - 如果$substr包含元字符，它们将像正则表达式修饰符一样工作。为了避免这种情况，你需要\b\Q$substr\E\b关闭metachar处理。