This is the program I came up with from your description (I hope it's what you meant). Problems are often better described with code, rather than English.
use strict;
use warnings;
my $variable = 1;
print $variable;
subroutine();
sub subroutine {
my $variable = 2;
print $variable;
}
#Output:
#12
Each print prints the value of the $variable it's closest to (in this example only, it's not a rule).
I fairly sure you will benefit from reading Coping with Scoping. It'll help you understand Perl's notion of global and local variables. | [reply]
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It depends on what scope the print statement falls into. Consider:
$foo = 'foo';
sub foo {
print $foo . "\n";
my $foo = 'bar';
print $foo . "\n";
}
foo;
which outputs:
foo
bar
Never do that in real code if you can help it.
Here, the scope of the global $foo is everywhere it's not masked by another variable with that name. Within the subroutine, it is only masked from the point the lexical $foo is declared until the end of the block. The sub has two different values for two different variables with the same name. That's a mess, and would be better avoided than implemented correctly. Implementing it correctly with the two variables named the same is just asking for someone to move the declaration of the lexical or the use of the global, and then you've got broken code.
You might not be able to control the naming of the global, but one would hope that you can control the name of the lexical. I would carefully name it something different. | [reply]
[d/l]
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Did you have something like this in mind?
#!/usr/bin/perl
use strict;
use warnings;
our $var = 'foo';
sub test {
my $var = 'bar';
print $main::var, "\n";
print "$var\n";
}
test();
Output:
foo
bar
Notes:
- You really shouldn't reuse variable names like this. As you have already discovered it makes debugging a lot more difficult and increases the likelihood of making mistakes.
- You should read up on 'our' to understand the full ramifications of using it (e.g. run perldoc -f our).
| [reply]
[d/l]
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| [reply] |
Depends on what you mean by "global" and "local", since perl doesn't really have those categories.
Perl does have lexical (declared with "my" and, in 5.10, "state") and package (declared with "our", "use vars", or "local") variables. Package variables are sometimes called "global" variables, but file-scoped
lexical variables sometimes are too. I don't know which you mean.
For variables of the same name, whichever was most recently declared in the lexical scope will be
what's used, whether by print or anything else, when you just say $variable. (Where "declared"
means via "my", "state", or "our".)
You can explicitly get a package variable by qualifying with the package name it was declared in,
where the default package is "main" (with the empty string as an alias). So $main::var (aka $::var)
will get the package variable, even if $var is a lexical at that point in your code.
I hope this helps you at least enough to rephrase your question. | [reply] |