... a method of changing several values at once.

I don't see this as a valid way of looking at this behavior. A hash key is always unique, and a hash key always has exactly one scalar value, although this scalar may be a reference to... well, anything, opening up vast possibilities for data structures, code dispatch tables, etc., etc., etc. So the only way to "[change] several values at once" is to replace a (scalar) reference to a bunch of stuff with another (scalar) reference to a different bunch of stuff.

Maybe one useful approximation to "changing several values at once", but with "changing" better understood as "dealing with", is the Perl idiom for implementing named, defaulted, non-positional function arguments. It goes something like: 

>perl -wMstrict -le
"sub D {
   my %defaults = qw(foo 999  bar 888  baz 777);
   ;;
   my ($hr_args) = @_;
   my %arguments = (%defaults, %{ $hr_args || {} });
   ;;
   print qq{foo $arguments{foo}  bar $arguments{bar}  baz $arguments{b
+az}};
   }
 ;;
 D();
 ;;
 D({bar => 2});
 ;;
 D({baz => 1, foo => 3});
"
foo 999  bar 888  baz 777
foo 999  bar 2  baz 777
foo 3  bar 888  baz 1

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In reply to Re: Hash assignment: Undocumented feature? by AnomalousMonk
in thread Hash assignment: Undocumented feature? by fsavigny

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