You're being bitten by the fact that 0 is false, so if you pass 0 in $db_write, the shift || 1 sees false || 1 and you get 1.

You will probably want to explicitely check for definedness instead:

my $ref_mail = shift;
my $db_write = shift;
# If $db_write is defined, use that, otherwise default to 1
$db_write = defined($db_write)?$db_write:1;
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Wow, thank you guys. That was really fast & you got my problem solved. Great community :)

This is exactly the kind of problem that the forthcoming "defined or" (//) operator is designed to deal with. If you're using the current development version of Perl (5.9) or when the next stable version (5.10) is released, you'll be able to write

my $db_write = shift // 1;
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Instead of

my $db_write = shift;
$db_write = 1 unless defined $db_write;
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Actually, I think that currently I'd write your code like this

my $ref_mail = shift;
my $db_write = @_ ? shift : 1;
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If you're using the current development version of Perl (5.9) or when the next stable version (5.10) is released, you'll be able to write

Or if you build a 5.8.x perl with the appropriate dor-* patch from http://perl.com/CPAN/authors/id/H/HM/HMBRAND/

Actually, I'd write it like that last way even with the // operator. It's just a good habit to be in for cases where undef actually is a legitimate value. For example, in a standard get/set object method, knowing that nothing is passed in (read-only) is a very different case from undef being passed in (setting the value to undef). Of course, I can't see using the ternary operator in that precise situation, just that it's an easy way to see the difference between no parameter and undef as a parameter.

Of course, there are times where I don't want undef as a valid value - but I want my use of // to be an explicit statement that undef isn't allowed rather than an unintentional default.

Actually, I think that currently I'd write your code like this

my $ref_mail = shift;
my $db_write = @_ ? shift : 1;
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That's icky, as it means more to change if there are ever more parameters than just these two. I'd suggest:

my $ref_mail = shift;
my $db_write = defined $_[0] ? shift : 1;
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<–radiant.matrix–>
A collection of thoughts and links from the minds of geeks
The Code that can be seen is not the true Code
I haven't found a problem yet that can't be solved by a well-placed trebuchet

Exactly! What if someone sent in something like this?

    foo(undef, 1, 2);
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Then the @_ version would shift off the undef, which is not what is wanted, I think.

Being contemplative
-v.

"Perl. There is no substitute."

my $db_write = shift || 1;
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#!/usr/bin/perl
use strict;
use warnings;

#=====================================================================
sub handleVoicemailNote {
#=====================================================================
    my ($ref_mail,$db_write) = @_;
    $db_write = 1 unless defined($db_write);
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Consider:

use warnings;
use strict;

my @lines;

test ("No switch param:");
test ("Switch param is 0", 0);
test ("Switch param is -1", -1);

sub test {
    my $param1 = shift;
    my $switch = shift || 1;
    
    print $param1;
    print " - Switch = $switch\n";
}
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Prints:

No switch param: - Switch = 1
Switch param is 0 - Switch = 1
Switch param is -1 - Switch = -1
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Note that 0 || 1 is 1.