The previous VPT 2020 workshop was organized in honour of Professor Alberto Pettorossi on the occasion of his academic retirement from Universit\`a di Roma Tor Vergata. Due to the pandemic the VPT 2020 meeting was cancelled but its proceeding have already appeared in the EPTCS 320 volume. The joint VPT-20-21 event has subsumed the original programme of VPT 2020 and provided an opportunity to meet and celebrate the achievements of Professor Alberto Pettorossi; its programme was further expanded with the newly submitted presentations for VPT 2021. The aim of the VPT workshop series is to provide a forum where people from the areas of program transformation and program verification can fruitfully exchange ideas and gain a deeper understanding of the interactions between those two fields.

翻译：在Alberto Pettorossi教授从Tor Vergata罗姆大学退休的学术退休之际,为他组织了上一次VPT 2020讲习班,由于这一流行病,VPT 2020会议被取消,但其进程已经载入ECTCS 320卷,VPT 20-21联合活动已纳入VPT 2020原方案,并提供机会会见和庆祝Alberto Pettorossi教授的成就;新提交的VPT 2021讲座进一步扩大了其方案;VPT 系列讲习班的目的是提供一个论坛,使来自方案转型和方案核查领域的人能够富有成效地交流意见,更深入地了解这两个领域之间的互动。