#!/usr/bin/perl
use strict;
use warnings;

sub defnz  {
    my @names = split /,/, shift;
    my %vars;
    @vars{@names} = @_;

    for my $item (@names) {
        if (!defined($vars{$item})) {
            print STDERR "$item is not defined\n";
            return;
        } elsif ($vars{$item} eq '') {
            print STDERR "$item is empty\n";
            return;
        }
    }
    print STDOUT "All scalars defined and non-empty\n";
    return 1; # all items in list defined and non-empty
}


my ($foo,$bar,$baz) = ("FOO","BAR","BAZ");
defnz('$foo,$bar,$baz', $foo,$bar,$baz);
($foo,$bar,$baz) = ("FOO","BAR","");
defnz('$foo,$bar,$baz', $foo,$bar,$baz);
($foo,$bar,$baz) = ("FOO",undef,"");
defnz('$foo,$bar,$baz', $foo,$bar,$baz);

__END__
output is:

All scalars defined and non-empty
$baz is empty
$bar is not defined
[download]

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

sub defnz  {
    my @names = split /,/, shift;
    my %vars;
    @vars{@names} = @_;

    for my $item (@names) {
        if (!defined($vars{$item}) || $vars{$item} eq '') {
            print STDERR Dumper(\%vars);
            return;
        }
    }
    print STDOUT "All scalars defined and non-empty\n";
    return 1; # all items in list defined and non-empty
}


my ($foo,$bar,$baz) = ("FOO","BAR","BAZ");
defnz('$foo,$bar,$baz', $foo,$bar,$baz);
($foo,$bar,$baz) = ("FOO","BAR","");
defnz('$foo,$bar,$baz', $foo,$bar,$baz);
($foo,$bar,$baz) = ("FOO",undef,"");
defnz('$foo,$bar,$baz', $foo,$bar,$baz);

__END__

output:

All scalars defined and non-empty
$VAR1 = {
          '$foo' => 'FOO',
          '$baz' => '',
          '$bar' => 'BAR'
        };
$VAR1 = {
          '$foo' => 'FOO',
          '$baz' => '',
          '$bar' => undef
        };
[download]

It is not possible to know the variable name of the variable passed into the subroutine ...

With Perl out of the box, that's true. Otherwise, use PadWalker.

Cheers,
Ovid

New address of my CGI Course.

use strict;
use warnings;

my $x = 10; 
my $y = undef; 
my $check = '$x,$y'; 
my @vars = split /,/,$check; 
for (@vars) { 
    if (defined(eval($_))) { 
        print "$_ = Defined\n"; 
    } else { print "$_ = Not defined\n";}
}
__END__
$x = Defined
$y = Not defined
[download]

There are risks associated with eval so you need to watch out

cheers

SK

Thanks! That was a cool solution. One caveat though, the variables to be checked must be visible (scope-wise) to the eval:

use strict;
use warnings;
 
my $foo = "1";
my $bar = "42";
 
my $defnz = sub {
  for (@_) {
    if (!defined(eval($_))) {
      print "$_ undef!";
      return;
    } elsif (eval($_) eq '') {
      print STDERR "$_ empty!";
      return;
    }
  }
  return 1;
};
 
my $baz = "101";
 
print "ok1\n" if &$defnz(split /,/,q($foo,$bar));
print "ok2\n" if &$defnz(split /,/,q($foo,$bar,$baz));
 
__END__
ok1
$baz undef!
[download]

Something silly...

You can use tie to follow your variable use during the run of your program.

Keep in mind that you can't directly access the name of the variable yourself, you have to pass the name as a parameter to your bound object.

The code would go like this:

Package Defined (Defined.PM)

package Defined;

use strict;
use warnings;

sub TIESCALAR { 
    my $class = shift;
    my $name = shift;
    my $self = { 'NAME' => $name,
             'DEFINED' => undef, };
    return bless ($self, $class);
}

sub FETCH {
    my $self = shift; 
    my $name = $self->{'NAME'}; 
    my @caller = caller; 
    if (defined $self->{'DEFINED'}) {
           print STDERR "@caller -> $name defined\n";
        } else {
         print STDERR "@caller -> $name undefined\n";
    }        
}

sub STORE {
    my $self = shift;
    my $value = shift;
    my $name = $self->{'NAME'};
    my @caller = caller;
    $self->{'DEFINED'} = $value;
    print STDERR "@caller -> $name defined with value $value\n";
}

1;
[download]

The caller (test.pl)

#!/usr/bin/perl

use Defined;

use strict;
use warnings;

my $var;
tie $var, 'Defined', '$var';

print $var;
$var = 1;
print $var;
$var = 5
[download]

Output

bash-3.00$ ./test.pl
main ./test.pl 11 -> $var undefined
main ./test.pl 12 -> $var defined with value 1
main ./test.pl 13 -> $var defined
main ./test.pl 14 -> $var defined with value 5
[download]

As I said, a bit silly. However, it might helpt in some cases of debugging.

HTH, --traveler