I'd avoid statement labels ('LINE' in your sample) unless they are required. Especially in a small scope the target of loop commands is clear in any case and adding statement labels makes it look like more is going on than is actually the case.

Bare in mind that the Perl documentation has evolved over a long period of time and has contributions from many people with different personal coding idioms. Some (much?) of the sample code in the Perl docs does not reflect common Perl idiom, but is a pragmatic way of illustrating some specific language feature. You will often see use of old style bare word file handles for example, or C style for loops. That doesn't mean that those style elements are current best practice however!