confused a little by use strict

[dan]

Howdy,

The code:

use strict;

my $foo = 0;

for $foo (0,1) {
print "$foo\n";
}

print "$foo\n";

outputs

0
1
0

So $foo comes out of the loop unchanged. OK, if thats how it works, then
why complain if I write

use strict;

my $foo = 0;

for $mistake (0,1) {
print "$foo\n";
}

print "$foo\n";

which outputs
Global symbol "$mistake" requires explicit package name ...?

Since it complains, this implies that in the first case, $foo would come
out of the loop with value 1, doesn't it?

 

[Gunnar Hjalmarsson]

The code:

use strict;
my $foo = 0;
for $foo (0,1) {
print "$foo\n";
}
print "$foo\n";

outputs

0
1
0

So $foo comes out of the loop unchanged.

The docs refer to it as "implicit localisation". Please read about
foreach loops in "perldoc perlsyn".

 

[Peter Scott]

use strict;

my $foo = 0;

for $foo (0,1) {
print "$foo\n";
}

print "$foo\n";

outputs

0
1
0

So $foo comes out of the loop unchanged. OK, if thats how it works, then
why complain if I write

use strict;

my $foo = 0;

for $mistake (0,1) {
print "$foo\n";
}

print "$foo\n";

which outputs
Global symbol "$mistake" requires explicit package name ...?

Since it complains, this implies that in the first case, $foo would come
out of the loop with value 1, doesn't it?

Your contention appears to be that since perl uses a 'temporary' variable
for the foreach iterator, shouldn't 'use strict' give it a pass if it's
not declared? The foreach semantics have evolved over the years and the
counterclaims to your argument are not as strong as they once were, but
nevertheless, at this point, perl elects to prefer to be consistent with
the "fully specify (or 'use vars') all package variables when using
strict" rule. Notice that if we turn strict off, we can see that perl
uses the package variable for the iterator if there's no lexical of the
same name (rather thab creating a new lexical):

$::foo = 'package';
for $foo ( 42 ) {
print "Package = $::foo\n";
}

# Package = 42

Just always say "for my ..." and you won't be bothered by these issues.