test.log

# puppet apply --parser=future --trusted_node_data  --test --stringify_facts  test.pp 
Info: Loading facts in /var/lib/puppet/lib/facter/ip6tables_version.rb
Info: Loading facts in /var/lib/puppet/lib/facter/apt_reboot_required.rb
Info: Loading facts in /var/lib/puppet/lib/facter/service_provider.rb
Info: Loading facts in /var/lib/puppet/lib/facter/apt_update_last_success.rb
Info: Loading facts in /var/lib/puppet/lib/facter/facter_dot_d.rb
Info: Loading facts in /var/lib/puppet/lib/facter/root_home.rb
Info: Loading facts in /var/lib/puppet/lib/facter/apt_updates.rb
Info: Loading facts in /var/lib/puppet/lib/facter/package_provider.rb
Info: Loading facts in /var/lib/puppet/lib/facter/puppet_vardir.rb
Info: Loading facts in /var/lib/puppet/lib/facter/pe_version.rb
Info: Loading facts in /var/lib/puppet/lib/facter/iptables_persistent_version.rb
Info: Loading facts in /var/lib/puppet/lib/facter/iptables_version.rb
Notice: em1,em3,em4,eth0,lo
Notice: eth0
Notice: [eth0]
Notice: Compiled catalog for xx.some.com in environment production in 0.75 seconds
Info: Applying configuration version '1481567209'
Notice: /Stage[main]/Main/File[/tmp/eth0]/ensure: defined content as '{md5}a1a5b3d22e82bbd6f878d26feacc2c7d'
Notice: Finished catalog run in 0.18 seconds

test.pp

$mac="01:01:01:01:01:01"

$found=[]
notice($facts["interfaces"])
$my_interfaces=split($facts["interfaces"],',')

$mac_interfaces=$my_interfaces.filter | $interface | {
  $facts["macaddress_${interface}"] == $mac 
}

$mac_interfaces.each | $interface | {
  notice($interface)
  file {"/tmp/${interface}":
                ensure => file,
                content => "$interface",
        }
}