Puppet - Variable for package name fails - puppet

Question

I'm new to puppet, and I am stumped.
I am installing gcc, gcc-c++, openssl and openssl-devel.
In the code shown, $openssl_devel works but $c_plus is undefined.
Why is puppet setting $c_plus to 'undef' ?
Cent OS 6
class torque::prerequisites {
case $operatingsystem {
centos,redhat: {$openssl_devel = 'openssl-devel'}
centos,redhat: {$c_plus = 'gcc-c++'}
debian,ubuntu: {$openssl_devel = 'libssl-dev'}
debian,ubuntu: {$c_plus = 'build-essential'}
default:{fail("Unable identify opperating system. $operatingsytem not recognized") }
}
package {'openssl':
ensure => latest,
}
package {$openssl_devel:
ensure => latest,
require => Package['openssl'],
}
package {'gcc':
ensure => installed,
}
package {$c_plus:
ensure => installed,
require => Package['gcc'],
}
}
class {'torque::prerequisites':}
puppet apply torque_prerequisites
err: /Stage[main]/Torque::Prerequisites/Package[undef]/ensure: change from absent to present failed: Could not find package undef

Answer 1

I still don't know why the original syntax didn't work, but this syntax does works:
class torque::prerequisites {
case $::osfamily {
Redhat: {
$openssl_devel = 'openssl-devel'
$c_plus_compiler = 'gcc-c++'
}
Debian: {
$openssl_devel = 'libssl-dev'
$c_plus_compiler = 'build-essential'
}
default:{fail("Unable identify opperating system. $operatingsytem not recognized") }
}
package {'openssl':
ensure => latest,
}
package {$openssl_devel:
ensure => latest,
require => Package['openssl'],
}
package {'gcc':
ensure => installed,
}
package {$c_plus_compiler:
ensure => installed,
require => Package['gcc'],
}
}
class {'torque::prerequisites':}