Here is your code:

print STDERR "$rec->[IMP_WG] $rec->[CSC_HAN]\n";
if ( defined( $rec->[IMP_WG] ) &&
     $rec->[IMP_WG] ne '' &&
     defined( $rec->[CSC_HAN] ) &&
     $rec->[CSC_HAN] eq '1' )
{
  print "$rec->[CLASSIF] $rec->[IMP_WG] $rec->[SRV_PLT]\n";
}
[download]

The print statement in the first line will be executed regardlessly. If in deed, $rec->[IMP_WG] and/or $rec->[CSC_HAN] are/is uninitialized, the warning you saw should be issued. To avoid this, simply test the values before you print, as you did in your second line.

#!/usr/bin/perl -w
use strict;
use Data::Dumper;

use constant index1 => 0;
use constant index2 => 1;

my $rec = [ undef, 1 ];
print Dumper($rec);                       # inspect before if

print "$rec->[index1] $rec->[index2]\n";  # warnings here (line 11)

if ( defined $rec->[index1] &&
     $rec->[index1] ne '' &&
     defined $rec->[index1] &&
     $rec->[index1] eq '1' )
{
    print "OK\n";
} else {
    print "Not OK\n";
}

print Dumper($rec);     # and check again after if
[download]

$VAR1 = [
          undef,
          1
        ];
Use of uninitialized value at ./p09.pl line 11.
 1
Not OK
$VAR1 = [
          undef,
          1
        ];
[download]

"I don't think your if test will autovivify anything because of the short circuit behaviour of the && operator."

It is true there is no autovivification, but it certainly has nothing to do with short circuit. If it should cause any autovivification, the first defined() call already triggered it, certainly no need for that 'ne' after the && to carry it out.

What autovivification says is that, read/test a non-exist element of a container, creates the ancestors of that node automatically. This is obviously not what is going on here.

Some definitions ...

use constant IMP_WG  => 18;
use constant CSC_HAN => 19;
[download]

And a dumped record with some data blanked out.

CSC.MIDRANGE.SERVER.SUPPORT 1
$VAR1 = [
          618,
          'xxxxxxxxxx',
          '3-Moderate',
          'Normal',
          'Closed',
          'xxxxxxxxxx',
          'xxxxxxxxxx',
          'Approved',
          'Approved',
          '05/12/03 10:00',
          '02/12/03 09:45',
          '3.00',
          'Successful',
          '12/12/03 09:53',
          '05/12/03 13:00',
          '05/12/03 09:52',
          'Midrange',
          'Production',
          'CSC.MIDRANGE.SERVER.SUPPORT',
          1
        ];
Use of uninitialized value at stats2 line 192.
[download]

As far as I can see in all cases the data I am testing does exist. I previously had the final test as $rec->[CSC_HAN] == 1 but that was one of the first things that I changed.

I cant see any scope for autovivification either ... the only possibility would be $rec but then the print statement should be throwing the uninitialised value errors.

If it matters (and it probably does with something this weird) $rec is a local copy of a pointer stored in a hash and obtained like so:

my $rec = $change_recs{$key};

What's SRV_PLT defined as?

I defined a new out of range index3 in the following example -


#!/usr/bin/perl -w
#use strict;
use Data::Dumper;

use constant index1 => 18;
use constant index2 => 19;
use constant index3 => 20;

my $rec = [
          618,
          'xxxxxxxxxx',
          '3-Moderate',
          'Normal',
          'Closed',
          'xxxxxxxxxx',
          'xxxxxxxxxx',
          'Approved',
          'Approved',
          '05/12/03 10:00',
          '02/12/03 09:45',
          '3.00',
          'Successful',
          '12/12/03 09:53',
          '05/12/03 13:00',
          '05/12/03 09:52',
          'Midrange',
          'Production',
          'CSC.MIDRANGE.SERVER.SUPPORT',
          1
        ];
# @$rec = map { defined($_) ? $_ : '' } @$rec;
# print Dumper($rec);

if ( defined $rec->[index1] &&
     $rec->[index1] ne '' &&
     defined $rec->[index2] &&
     $rec->[index2] eq '1' )
{
    if ($rec->[index3] == 1) { print "Crap\n" };                    # 
+39
    print "$rec->[index1] $rec->[index2] ", $rec->[index3], "\n";   # 
+40
    print "OK\n";
} else {
    print "Not OK\n";
}

# print Dumper($rec);
[download]


And the output of an out of range index3:


Use of uninitialized value at ./p09.pl line 39.
Use of uninitialized value at ./p09.pl line 40.
CSC.MIDRANGE.SERVER.SUPPORT 1
[download]

$rec->[IMP_WG]    = defined $rec->[IMP_WG]  ? $rec->[IMP_WG]  : '';
$rec->[CSC_HAN]   = defined $rec->[CSC_HAN] ? $rec->[CSC_HAN] : '';
$rec->[CLASSIF]   = defined $rec->[CLASSIF] ? $rec->[CLASSIF] : '';
$rec->[SRV_PLT]   = defined $rec->[SRV_PLT] ? $rec->[SRV_PLT] : '';

print STDERR "$rec->[IMP_WG] $rec->[CSC_HAN]\n";

if ( $rec->[IMP_WG] ne '' && $rec->[CSC_HAN] eq '1' )
{
  print "$rec->[CLASSIF] $rec->[IMP_WG] $rec->[SRV_PLT]\n";
}
[download]

--
Tommy Butler, a.k.a. TOMMY

Too much typing, you could do with a one-liner instead. I ++'ed you anyhow because the idea is good. ;-)


use strict;
use Data::Dumper;

my $rec = [ undef, 1, '', 2, 0 ];

@$rec = map { defined($_) ? $_ : '' } @$rec;

print Dumper($rec);

__END__

# ---output ---
$VAR1 = [
          '',
          1,
          '',
          2,
          '0'
        ];
[download]

Thanks Roger :o)

--
Tommy Butler, a.k.a. TOMMY

Is it possible that you have an elsif clause? Use of an undef value in it will produce a warning giving the line number of the if, since that is the beginning of the statement.