If you want to store a %ENV value in SSI Web 7, the best option may be to add a free format question to your questionnaire with a hidden variable. Then you can give the free format HTML like this:
<input name="[% QuestionName() %]_ffvar" id="[% QuestionName() %]_ffvar" type="hidden" value="[% Begin Unverified Perl
End Unverified %]"/>
"ffvar" must be replaced with the name of the hidden free format variable. "envvar" must be replaced with the name of the environment variable to be stored.