use Data::Dumper;
my $val = 'something';
print Dumper(\$val);
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lanx@nc10-ubuntu:~$ perl
use Data::Dump qw/pp/;
$x=[1,2,3];
pp $x;
pp $a;
__END__
[1, 2, 3]
undef
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If you want undefined values printed as "undef", try

use 5.010;
print $somevalue // "undef";
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... noting that the "//" operator is, IIRC, a relatively recent addition to the language.   You should have it, but you (or some backwater web-hosting companies who need not be named ...) conceivably might not.   See perldoc perlop on your system; look for the heading “C-style Logical Defined-Or.”

See that first line in my the code? It says use 5.010;. The // operator was new in perl 5.10. It's not new anymore now.

> ... noting that the "//" operator is, IIRC, a relatively recent addition to the language.

Googling perldelta defined-or quickly leads to http://perldoc.perl.org/5.10.0/perldelta.html#Defined-or-operator

(update: Perl 5.10.0 released Dec 2007)

So even if you ignore ambrus' use 5.010 there is no need to "IIRC" instead of checking!

> See perldoc perlop on your system; look for the heading “C-style Logical Defined-Or.”

see What shortcuts can I use for linking to other information?

Cheers Rolf

( addicted to the Perl Programming Language)

sub safe_print {
    for my $item (@_) {
        print defined $item ? $item : '[undef]';
    }
}
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sub safe_print {
    local $_;
    print map { defined $_ ? $_ : '[UNDEF]' } @_;
}
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use strict;
use warnings;

sub new {
    my($class, $args) = @_;
    $args = {} unless defined $args;
    die "Arguments must be a hash ref\n" unless ref($args) eq 'HASH';
    my $self = { %$args };
    bless $self, $class;
    return $self;
}

sub print {
    my $self = shift;
    $self->{fh} = *STDOUT unless defined $self->{fh};
    my $fh = $self->{fh};
    print $fh (map { defined $_ ? $_ : '[UNDEF]' } @_);
}
1;
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open my $fh, ">", "foo" or die "Can't open foo: $!\n";
my $printer = SafePrinter->new({fh => $fh});
$printer->print("so it goes", undef, 'and it went', "\n");
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