Try using a hash with the named params as keys like this: 

my %session_params = (
    hostname      => $ARGV[0],
    port          => $ARGV[6],
    version       => $ARGV[5] ? "snmpv" . $ARGV[5] : '',
    timeout       => $ARGV[7],
    ... # and so on for all params
};

for ( keys( %session_params ) {
    delete( $session_params{$_} unless $session_params{$_};
}

my ( $session, $error ) = Net::SNMP->session( %session_params );

# Update:
# allowed for an empty string for an arg that was being manipulated: $
+ARGV[5]

[download]
This is a very simple example, but I think you get the idea. You can see how I use a similar approach which includes setting default values if you view the source for DateTimeX::Fiscal::Fiscal5253.

I would consider using Getopt::Long and have named params on the command line to make life a little bit easier.

Update: Here is the direct solution to what you gave: 

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

my $foo = 1;
my $bar = 'baz';
my $baz = '';

my %foohash = (
    $foo ? ( foo => $foo ) : (),
    bar => $bar,
    $baz ? ( baz => $baz ) : (),
    $ARGV[0] ? ( version => 'snmpv' . $ARGV[0] ) : ()
);

print Dumper(\%foohash);

exit;

__END__

Output:
$VAR1 = {
          'bar' => 'baz',
          'foo' => 1
        };

[download]

No matter what approach you take, I strongly advise doing some parameter validation before using them!

You must always remember that the primary goal is to drain the swamp even when you are hip-deep in alligators.

In reply to Re: Optionally include named arguments when constructing a new object by boftx
in thread Optionally include named arguments when constructing a new object by nice_iguana

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