是否应该忽略符号与其变量名称之间的空格? [英] Is space supposed to be ignored between a sigil and its variable name?
问题描述
我刚刚发现 perl 忽略了 sigil 和它的变量名之间的空格，想知道是否有人能告诉我这是否是预期的行为.我以前从未遇到过这种情况，它可能会导致字符串内部出现奇怪的行为.
I just discovered that perl ignores space between the sigil and its variable name and was wondering if someone could tell me if this was the expected behaviour. I've never run into this before and it can result in strange behaviour inside of strings.
例如，在下面的代码中，$bar 将以值 'foo' 结束:
For example, in the following code, $bar will end up with the value 'foo':
my $foo = 'foo';
my $bar = "$ foo";
这也适用于变量声明:
my $
bar = "foo\n";
print $bar;
第二种情况对我来说并不重要，但在字符串插值的情况下，这可能会导致非常混乱的行为.有人知道这件事吗?
The second case doesn't really matter much to me but in the case of string interpolation this can lead to very confusing behaviour. Anyone know anything about this?
推荐答案
是的，它是语言的一部分.不，您不应该将它用于严肃的代码.至于插值的混乱，所有美元符号(不是变量的一部分)都应该被转义，而不仅仅是字母旁边的那些，所以这应该不是问题.
Yes, it is part of the language. No, you should not use it for serious code. As for being confusing in interpolation, all dollar signs (that are not part of a variable) should be escaped, not just the ones next to letters, so it shouldn't be a problem.
我不知道这是否是允许在 sigil 和变量名称之间使用空格的真正原因，但它允许您执行诸如
I do not know if this is the real reason behind allowing whitespace in between the sigil and the variable name, but it allows you to do things like
my $ count = 0;
my $file_handle_foo = IO::File->new;
某些人可能会认为这很方便(因为它将符号和变量名称的唯一部分放在一起).它对于 Obfu 也很有用(参见第 9 行的结尾和第 10 行的开头):
which might be seen by some people as handy (since it puts the sigils and the unique parts of the variable names next to each other). It is also useful for Obfu (see the end of line 9 and beginning of line 10):
#!/usr/bin/perl -w # camel code
use strict;
$_='ev
al("seek\040D
ATA,0, 0;");foreach(1..3)
{<DATA>;}my @camel1hump;my$camel;
my$Camel ;while( <DATA>){$_=sprintf("%-6
9s",$_);my@dromedary 1=split(//);if(defined($
_=<DATA>)){@camel1hum p=split(//);}while(@dromeda
ry1){my$camel1hump=0 ;my$CAMEL=3;if(defined($_=shif
t(@dromedary1 ))&&/\S/){$camel1hump+=1<<$CAMEL;}
$CAMEL--;if(d efined($_=shift(@dromedary1))&&/\S/){
$camel1hump+=1 <<$CAMEL;}$CAMEL--;if(defined($_=shift(
@camel1hump))&&/\S/){$camel1hump+=1<<$CAMEL;}$CAMEL--;if(
defined($_=shift(@camel1hump))&&/\S/){$camel1hump+=1<<$CAME
L;;}$camel.=(split(//,"\040..m`{/J\047\134}L^7FX"))[$camel1h
ump];}$camel.="\n";}@camel1hump=split(/\n/,$camel);foreach(@
camel1hump){chomp;$Camel=$_;y/LJF7\173\175`\047/\061\062\063\
064\065\066\067\070/;y/12345678/JL7F\175\173\047`/;$_=reverse;
print"$_\040$Camel\n";}foreach(@camel1hump){chomp;$Camel=$_;y
/LJF7\173\175`\047/12345678/;y/12345678/JL7F\175\173\0 47`/;
$_=reverse;print"\040$_$Camel\n";}';;s/\s*//g;;eval; eval
("seek\040DATA,0,0;");undef$/;$_=<DATA>;s/\s*//g;( );;s
;^.*_;;;map{eval"print\"$_\"";}/.{4}/g; __DATA__ \124
\1 50\145\040\165\163\145\040\157\1 46\040\1 41\0
40\143\141 \155\145\1 54\040\1 51\155\ 141
\147\145\0 40\151\156 \040\141 \163\16 3\
157\143\ 151\141\16 4\151\1 57\156
\040\167 \151\164\1 50\040\ 120\1
45\162\ 154\040\15 1\163\ 040\14
1\040\1 64\162\1 41\144 \145\
155\14 1\162\ 153\04 0\157
\146\ 040\11 7\047\ 122\1
45\15 1\154\1 54\171 \040
\046\ 012\101\16 3\16
3\15 7\143\15 1\14
1\16 4\145\163 \054
\040 \111\156\14 3\056
\040\ 125\163\145\14 4\040\
167\1 51\164\1 50\0 40\160\
145\162 \155\151
\163\163 \151\1
57\156\056
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