Well, it is dangerous in the sense that it is only, IMHO, a partial separation of Perl and HTML. As a pragmatic point I consider that the programme and the presentation should 'always be separated when it is reasonably possible to do so'
The viewpoint I was hoping to express here is that if this technique works for you, then use it. But beware, it is only a half measure and wilst I would consider it appropriate for small or simple applications. I think the original question included a remark about the writer preparing some scripts for a friend where a simple script and a single template were involved. As a method of packaging the script and template where the author is likely to be the one modifying both parts then it might be a pragmatically acceptable alternative.