All branches matching this regular expression are considered perennial branches.

configure in config file

In the config file the perennial regex exists inside the [branches] section:

perennial-regex = "release-*"

configure in Git metadata

You can configure the perennial branches manually by running:

git config [--global] git-town.perennial-regex 'release-.*'

The optional --global flag applies this setting to all Git repositories on your local machine. When not present, the setting applies to the current repo.