string Perl 中的单引号和双引号有什么区别？
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What's the difference between single and double quotes in Perl?
提问by chappar
In Perl, what is the difference between 'and "?
在 Perl 中，'和之间有什么区别"？
For example, I have 2 variables like below:
例如，我有 2 个变量，如下所示：
$var1 = '\(';
$var2 = "\(";
$res1 = ($matchStr =~ m/$var1/);
$res2 = ($matchStr =~ m/$var2/);
The $res2statement complains that Unmatched ( before HERE mark in regex m.
该$res2声明中抱怨说Unmatched ( before HERE mark in regex m。
回答by Xetius
Double quotes use variable expansion. Single quotes don't
双引号使用变量扩展。单引号不
In a double quoted string you need to escape certain characters to stop them being interpreted differently. In a single quoted string you don't (except for a backslash if it is the final character in the string)
在双引号字符串中，您需要对某些字符进行转义以阻止它们被不同地解释。在单引号字符串中你没有（反斜杠除外，如果它是字符串中的最后一个字符）
my $var1 = 'Hello';
my $var2 = "$var1";
my $var3 = '$var1';
print $var2;
print "\n";
print $var3;
print "\n";
This will output
这将输出
Hello
$var1
Perl Monks has a pretty good explanation of this here
Perl Monks 对此有很好的解释here
回答by Chaos
' will not resolve variables and escapes
' 不会解析变量和转义
" will resolve variables, and escape characters.
" 将解析变量，并转义字符。
If you want to store your \ character in the string in $var2, use "\\("
如果要将 \ 字符存储在 $var2 的字符串中，请使用 "\\("
回答by Silfverstrom
Double quotation marks interpret, and single quotation do not
双引号解释，单引号不解释
回答by Igor Krivokon
Perl takes the single-quoted strings 'as is' and interpolates the double-quoted strings. Interpolate means, that it substitutes variables with variable values, and also understands escaped characters. So, your "\(" is interpreted as '(', and your regexp becomes m/(/, this is why Perl complains.
Perl 接受单引号字符串“原样”并插入双引号字符串。插值意味着，它用变量值替换变量，并且还理解转义字符。所以，你的 "\(" 被解释为 '('，你的正则表达式变成了 m/(/，这就是 Perl 抱怨的原因。
回答by Chas. Owens
If you are going to create regex strings you should really be using the qr// quote-like operator:
如果您要创建正则表达式字符串，您真的应该使用qr// 类似引号的运算符：
my $matchStr = "(";
my $var1 = qr/\(/;
my $res1 = ($matchStr =~ m/$var1/);
It creates a compiled regex that is much faster than just using a variable containing string. It also will return a string if not used in a regex context, so you can say things like
它创建了一个编译的正则表达式，它比仅使用包含字符串的变量快得多。如果不在正则表达式上下文中使用，它也会返回一个字符串，因此您可以这样说
print "$var1\n"; #prints (?-xism:\()
回答by Canopus
"" Supports variable interpolation and escaping. so inside "\("\escapes (
"" 支持变量插值和转义。所以里面"\("\逃逸（
Where as ' ' does not support either. So '\('is literally \(
其中 ' ' 也不支持。'\('从字面上看也是如此\(
