They are by no means 'bad practice'. They are just a way to make subroutine start/end points visually obvious when scanning code. I use them routinely myself. If I were to find a good 'tree collapsing' editor for Perl, I would probably stop using them. But it is just someone's personal preference to declare them 'obnoxious'. It doesn't actually rise to the level of something that should be spit out by Perl::Critic as an issue.
Many programmers are obsessively anal retentive about details. It's a positive skill when applied to 'code correctness'. But it easily turns into pointless rules where simple personal preference is elevated into 'The Way It Is Done (tm)'.