using local variables

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I am using local vaiables in a sub. But with @wire2 it is not working. The history of this variable is keept like I would expect it for a global variable.

#!/usr/bin/perl 

 wr_module("1");
 wr_module("2");
 wr_module("3");
 exit;


sub wr_module 
{ my $x=shift;
  my $wire0;
  my @wire1;
  my @wire2;
  print("Adding $x ");  
  $wire0.=$x;
  $wire1[1].=$x;
  $wire2{"a"}.=$x;
  print(" => $wire0 :: $wire1[1] :: $wire2{\"a\"} \n");
}
[download]

The script returns:

Adding 1  => 1 :: 1 :: 1 
Adding 2  => 2 :: 2 :: 12 
Adding 3  => 3 :: 3 :: 123
[download]

I would expect:

Adding 1  => 1 :: 1 :: 1 
Adding 2  => 2 :: 2 :: 2 
Adding 3  => 3 :: 3 :: 3
[download]

Do you have an idea, why the "my" is not working for @wire2 ? Thanks for your help !

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Re: using local variables by Corion (Patriarch) on Mar 16, 2016 at 10:24 UTC
Perl can help you a lot with your code if you let it. In your case, adding the line `use strict;` near the top of your program will make Perl tell you about undeclared variables. In your case, you're declaring a variable `@wire2` as an array, but you are actually using a hash `%wire2` in the line: `$wire2{ "a"} .= $x;` [download] This is why it's always recommended that you add the two lines near the top of your scripts: `use strict; use warnings;` [download]	[reply] [d/l] [select]
Re^2: using local variables by Anonymous Monk on Mar 16, 2016 at 10:37 UTC
Thanks. That helped me a lot.	[reply]
Re: using local variables by Eily (Monsignor) on Mar 16, 2016 at 10:30 UTC
For your information, when a single word is used as the key in a hash, perl allows you to omit the quotes. So `$wire2{"a"}` and `$wire2{a}` are equivalent, and `"$wire2{a}"` does what you want. And ++ to Corion for strictures and warnings.	[reply] [d/l] [select]