This is a boiled-down version of a bit of sofware where I discovered I
apparently don't fully understand variable scopes. In the following,
the "our" variable $request will be undef in the unnamed Start
subroutine if I just try to define it with "my". Apparently using it in
foreach is the cause, but I am a bit unclear on how/why this happens?

Anyone have pointers to web pages etc where this is spelled out?

Also, using a global variable here is obviously kludgy. Forgive me.

----

#!/usr/bin/perl
use strict;
use warnings;
use XML::Parser::Lite;

my $xmldata = <<'END';
<response>
<record value="first"/>
<record value="second"/>
</response>
END

our $request;

my $parser = XML::Parser::Lite->new(
Handlers => {
Start => sub {
shift;
# Only process "record" blocks
return unless shift eq 'record';
# Load parsed xml into hash for access
my %data=@_;
print $request,"\t",$data{'value'},"\n";
},
},
);

foreach $request ( qw(datarequest) ) {
# Here we would retrieve xml data from SOAP using $request etc
$parser->parse($xmldata);
}

--
/* * * Otto J. Makela <om@iki.fi> * * * * * * * * * */
/* Phone: +358 40 765 5772, ICBM: N 60 10' E 24 55' */
/* Mail: Mechelininkatu 26 B 27, FI-00100 Helsinki */
/* * * Computers Rule 01001111 01001011 * * * * * * */

On Tuesday, October 25, 2022 at 2:38:06 PM UTC+2, Otto J. Makela wrote:
> This is a boiled-down version of a bit of sofware where I discovered I
> apparently don't fully understand variable scopes. In the following,
> the "our" variable $request will be undef in the unnamed Start
> subroutine if I just try to define it with "my". Apparently using it in
> foreach is the cause, but I am a bit unclear on how/why this happens?
>
> Anyone have pointers to web pages etc where this is spelled out?
>
> Also, using a global variable here is obviously kludgy. Forgive me.
>
> ----
>
> #!/usr/bin/perl
> use strict;
> use warnings;
> use XML::Parser::Lite;
>
> my $xmldata = <<'END';
> <response>
> <record value="first"/>
> <record value="second"/>
> </response>
> END
>
> our $request;
>
> my $parser = XML::Parser::Lite->new(
> Handlers => {
> Start => sub {
> shift;
> # Only process "record" blocks
> return unless shift eq 'record';
> # Load parsed xml into hash for access
> my %data=@_;
> print $request,"\t",$data{'value'},"\n";
> },
> },
> );
>
> foreach $request ( qw(datarequest) ) {
> # Here we would retrieve xml data from SOAP using $request etc
> $parser->parse($xmldata);
> }
>
> --
> /* * * Otto J. Makela <o...@iki.fi> * * * * * * * * * */
> /* Phone: +358 40 765 5772, ICBM: N 60 10' E 24 55' */
> /* Mail: Mechelininkatu 26 B 27, FI-00100 Helsinki */
> /* * * Computers Rule 01001111 01001011 * * * * * * */

The code can be simplified, you don't need the XML parser to demonstrate the behaviour:

#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

# Replace "our" with "my".
our $request = 10;

my $print = sub { say 'print ', \$request, ": $request" };

for $request (12) {
say 'for ', \$request, ": $request";
$print->();
}

You can see the *address* of the variable is different when you use my. I'm not sure it's the expected behaviour, though, as the documentation says:

| If the variable was previously declared with "my", it uses that variable instead of the global one, but it's still localized to the loop.

I've never used "for/foeach $var" without "my". It's a good habit to get into and you then just need to assign the actual iteration value to the outer closed over variable.

#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

my $request = 10;

my $print = sub { say 'print ', \$request, ": $request" };

for my $r (12) {
$request = $r;
say 'for ', \$request, ": $request";
$print->();
}

E. Choroba

with <87eduwkriv.fsf@tigger.extechop.net> Otto J. Makela wrote:

*SKIP*
> Also, using a global variable here is obviously kludgy. Forgive me.

I hope this horse is already dead and doesn't deserve any more beating.

*CUT*

--
Torvalds' goal for Linux is very simple: World Domination
Stallman's goal for GNU is even simpler: Freedom