Whether or not there are "legal issues" with "Purl" being confusingly similar to "Perl" would be up the judgement of a court, should it come to that.
Mostly, when there are other open source projects whose names conflict with your trademark you ask nicely and people change the name. That's the path I'm hoping to guide the OP down — please just have some sympathy for your fellow open source developers!
Occasionally, trademark conflicts in open source become high stakes, painful affairs. For example, with the last few years, there was the "Commons Clause" situation (where among other issues "Apache License Version 2 with Commons Clause" infringed upon the "Apache" trademark owned by the ASF.)
This is unlikely to become a problem with a solo personal project unless it gains sustained traction. But I think it's valid feedback to offer, because if you have ambitions for your open source project you are eventually going to have to deal with trademarks.
Mostly, when there are other open source projects whose names conflict with your trademark you ask nicely and people change the name. That's the path I'm hoping to guide the OP down — please just have some sympathy for your fellow open source developers!
Occasionally, trademark conflicts in open source become high stakes, painful affairs. For example, with the last few years, there was the "Commons Clause" situation (where among other issues "Apache License Version 2 with Commons Clause" infringed upon the "Apache" trademark owned by the ASF.)
This is unlikely to become a problem with a solo personal project unless it gains sustained traction. But I think it's valid feedback to offer, because if you have ambitions for your open source project you are eventually going to have to deal with trademarks.