The @+ and @- variables allow you to reference capture buffers by index rather by named variables (e.g. substr($var, $-[2], $+[2] - $-[2]) rather than $2). Similarly %+ allows access to named captures by "index" (the name).

$ perl5.10.0 -E '$_="ab cd ef gh";m/(?<foo>\S+)\s+\S+\s+(?<bar>\S+)/; 
+for(keys %+){say "$_:\t$+{$_}"}; say "\$+: $+";'
bar:    ef
foo:    ab
$+: ef
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It's not like $+ which is a special name for "whatever the last group was which matched"; $+ always going to refer to whatever the last group was which successfully matched, whereas %+ allows access to all of the named captures.

That clear things up?

Update: Oop, had @+ twice first sentence; thanks linuxer.

Yes, that cleared it up. Thanks for that.

Ok, though I understand that now, I think, that "similar to @+" should be rephrased to be more concrete what is meant (or may it even be left out? Is it really necessary?).

added:

If I read perlvar from the beginning to end, as we can see, I don't recognize this "similarity" of @+ and %+. @- is explained a few paragraphes later in the document, so hasn't been read yet. I don't think, it's clear enough (in the doc).

I understand what it's saying, but I also can understand why it's not readily apparent (especially to a non-native speaker) because I'm having a hard time coming up with a clearer phrasing for it myself :). Maybe "Analogous to @+ for accessing captures via numeric indexes, %+ allows accessing named captures via the name"? If you want to access captures by their index, use @+ and @-; if you want to access (named) captures by name, use %+.

The cake is a lie.
The cake is a lie.
The cake is a lie.

Similar to @+, the %+ hash allows access to the named capture buffers

@+ provides access to all capture buffers (not just the named ones), so the statement is unclear if not incorrect.

@+ is about "offsets of the ends of the last successful submatches" and %+ about accessing "named capture buffers". How can these two things be similar?

perlvar only claimed that one aspect was similar. It never said the kind of access to the capture buffers was similar. That one variable provides the offset of the end of the buffer while the other provides the contents of the buffer does not disprove the claim of similarity that perlvar made.