May be a hash would be better

my %h = (
         ipaddress  => "foo_0",
         username   => "foo_1",
         password   => "foo_2",
         sessionid  => "foo_3",
         version    => "foo_4",
);

sub foo {
        my $parameter = $_[0];
        print "\nParameter: $parameter\n";

        die "Bad parameter $paramenter"
          unless exists $h{$parameter};

        return $h{$parameter};
}

my $returned = &foo(@ARGV[0]);
print "Returned: $returned\n";
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