Here's a very small example code:
Bedroom is a room. "This is your bedroom."
The bed is a scenery enterable supporter in the bedroom.
When play begins:
now the player is on the bed.
The result is:
Bedroom (on the bed)
This is your bedroom.
Welcome
An Interactive Fiction
Release 1 / Serial number 150823 / Inform 7 build 6L38 (I6/v6.33 lib 6/12N) SD
Bedroom (on the bed)
This is your bedroom.
It shows Bedroom description twice when I put the player on the bed.