Host mygateway-www
Hostname www
IdentityFile ~/.ssh/id_rsa
ProxyCommand ssh mygateway nc %h 22

Host mygateway-*
Hostname ???WHAT GOES HERE????
IdentityFile ~/.ssh/id_rsa
ProxyCommand ssh mygateway nc %h 22

Host *
  ServerAliveInterval 120

Host gateway.somewhere.com
  User jdoe

Host gateway+*
  User jdoe
  ProxyCommand ssh -T -a $(echo %h |cut -d+ -f1).somewhere.com nc $(echo %h |cut -d+ -f2) %p 2>/dev/null
  ControlMaster auto
  ControlPath ~/.ssh/ssh-control_%r@%h:%p

ssh gateway+internalhost01.somewhere.com
ssh gateway+internalhost02.somewhere.com

Host *.domain
  IdentityFile ~/.ssh/id_rsa
  ProxyCommand ssh mygateway /usr/bin/nc %h 22

Host mygateway-*
   #Hostname ???WHAT GOES HERE????
   IdentityFile ~/.ssh/id_rsa
   ProxyCommand ssh mygateway nc $(echo %h|sed 's/^mygateway-//') %p

Host *-*
   # Assume LHS of "-" is GW and RHS of "-" is target host
   IdentityFile ~/.ssh/id_rsa
   ProxyCommand ssh $(echo %h|cut -d - -f1) nc $(echo %h|cut -d - -f2-) %p

Host *-*
   # Assume LHS of "-" is GW and RHS of "-" is target host
   IdentityFile ~/.ssh/id_rsa
   ProxyCommand ssh -W $(echo %h|cut -d - -f2-):%p $(echo %h|cut -d - -f1)

Host host1 host2 host3 hostN
   IdentityFile ~/.ssh/id_rsa
   ProxyCommand ssh mygateway nc %h %p