How can I use variable on NSIS include / to get another variable

How can I use variable on NSIS include / to get another variable

Is there anyway to include file by mention it with variable? I mean
StrCpy $1 "bla.nsh"
!include $1
?
or maybe getting value of variable that called by another variable such as:
StrCpy $1 "EN"
StrCpy $2 ${LANG_${1}_WELCOME_MESSAGE}
?
Thanks.