Pershing Square is preparing a new fund called Pershing Square Ventures to give investors access to private equity and pre-IPO companies, joining a broader push by investment firms to offer exposure to high-growth startups before they list publicly. The vehicle is being structured as an evergreen, permanent-capital fund, allowing it to keep holdings for the long term and retain shares after portfolio companies go public. Bill Ackman and Chief Investment Officer Ryan Israel said in a shareholder letter on Wednesday that Pershing Square Inc. has begun the process of establishing Pershing Square Ventures Ltd. The letter said Pershing Square recently completed several investments in private companies, and those positions will form part of the new fund’s initial portfolio.