Mention that the regex used by the empty m// is scoped

[choroba]

No description provided.

[demerphq]

FWIW perlvar already contains the following text:

Notice that each successful match in the exact same scope overrides the
match context of the previous successful match, but that unsuccessful
matches do not. Also note that in an inner nested scope the previous
state from an outer dynamic scope persists until it has been overriden
by another successful match, but that when the inner nested scope exits
whatever match context was in effect before the inner successful match
is restored when the scope concludes.

It is a known issue that goto LABEL may interact poorly with the
dynamically scoped match context. This may not be fixable, and is
considered to be one of many good reasons to avoid goto LABEL.