为什么在此Perl代码中出现“'$ rocks ['附近的语法错误””？

Question

When I run this program on ActivePerl 5.8 on Windows XP, I get a syntax error:

#!C:\Perl\bin\perl.exe

use strict; # enabled
use warnings;


(my $rocks[0], my $rocks[1]) = qw/Hello World/; # Syntax error near '$rocks['

my $rocks[2] = 'Tom'; # Syntax error near '$rocks['
my $rocks[3] = 'Cat'; # Syntax error near '$rocks['

print $rocks[0];
print $rocks[1];
print $rocks[2];
print $rocks[3];

When I used ( @ ) before the name of the array rocks , it worked well. How do I fix the error above when I used $ ? Thank you.

my @rocks = qw{Hello World Tom Cat}; # worked well.

Answer 1

Don't use my again and again to declare $rocks[0] , $rocks[1] etc. Declare the array once ( @rocks ) and use it.

The corrected code is something like this:

use strict;
use warnings; 
my @rocks; ## declare the array here

($rocks[0], $rocks[1]) = qw/Hello World/; 
$rocks[2] = 'Tom'; 
$rocks[3] = 'Cat';

Answer 2

Use the push operator:

my @rocks;

push @rocks, qw/ Hello World /;
push @rocks, "Tom";
push @rocks, "Cat";

Avoiding explicit and redundant array indices helps future-proof your code. For example, if you find you need to change your initialization, you can't botch an array index that isn't there.

Answer 3

I think you need to declare my @rocks and then not use my any more when referring to $rocks[xxx] .

If you don't know how many elements are going to be in there, you can use push to add new elements into the (initially 0-sized) array.

Answer 4

You are redeclaring @rocks several times. Try something like this instead:

my @rocks;

$rocks[0] = 'Tom';
$rocks[1] = 'Cat';

etc.

Answer 5

You can first declare the array at the top as:

my @rocks;

And remove my declaration from all other places.

Your code becomes:

#!C:\Perl\bin\perl.exe
# ActivePerl 5.8 based
use strict; # enabled
use warnings;

my @rocks;

($rocks[0], $rocks[1]) = qw/Hello World/; # Syntax error near '$rocks['

$rocks[2] = 'Tom'; # Syntax error near '$rocks['
$rocks[3] = 'Cat'; # Syntax error near '$rocks['

print $rocks[0];
print $rocks[1];
print $rocks[2];
print $rocks[3];

Answer 6

Why don't you just put it straight into @rocks ?

use strict;
use warnings;



my $rocks[2] = 'Tom';
my $rocks[3] = 'Cat';

print $rocks[0];
print $rocks[1];
print $rocks[2];
print $rocks[3];