Regex for restricting branch name on merge denies all

GitLab documentation refers users to Rubular for checking regex expressions, however the below expressions for restricting branch names on merge is denied upon merge attempt saying,

GitLab: Branch name does not follow the pattern ‘\A(feature|hotfix|bug)/\S[a-z-]+\z’

Branch name: feature/sort-and-display-assignment-list

Expressions attempted:

Please refer to this summary example: