debian package installation - setting environment

[Ivars Strazdins <ivars.strazdins@sets.lv>]

Hello all,
how do I set/change system wide environment variables when installing 
package?

The package should go to /opt/<packagename>. I've been reading a lot of 
fighting about /opt for packages. Anyway, this seem to be the right 
place for 3rd party packages. Also, I cannot change this  decision anyway :(

So, I need at least to add /opt/<package>/bin to $PATH + maybe setting 
some other environment variables (creating a wrapper script in $PATH is 
another possibility). How do I do this?

This seem to be appropriate mailing list, please advice, if not.
with kind regards,

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