helper_dir="$(mktemp -d -t travis-perl-helpers-XXXXXX)";
git init "$helper_dir";
(
  cd "$helper_dir";
  git remote add origin "${TRAVIS_PERL_REPO:-https://github.com/travis-perl/helpers.git}";
  branch="${TRAVIS_PERL_BRANCH:-master}";
  [[ "$branch" == pull-request/* ]] && refspec="refs/pull/${branch:13}/head" || refspec="refs/heads/$branch";
  git fetch origin --depth=1 "$refspec:refs/remotes/origin/$branch";
  git checkout -b "$branch" "origin/$branch";
);
source "$helper_dir/init"