Setting and environment variable for one specific subdomain matching the ServerAlias

I have a virtual host that includes the following settings

Ser开发者_StackOverflow社区verName www.host.com
ServerAlias *.host.com

Can I set

SetEnv FOO "bar"

for just a specific subdomain (like foo.host.com)?

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The answer is the SetEnvIf directive:

SetEnvIf Host .*foo\.host\.com FOO=bar