use Data::Dumper;

my $h = f(qw[ foo => zoo moo too
              bar => car far
              bar => zar tar
              qux => mux ]);


print Dumper $h;

sub f {
  $_='';my@v;{$_&&push@v,$_;$_=pop;redo until/=>/}
  $k=pop;$h{$k}=[@v,@{$h{$k}}];@_?&f:\%h
}

##</code><code>##

sub f {
  $_=my@v;{$_&&push@v,$_;$_=pop;/=>/||redo}
  $k=pop;$h{$k}=[@v,@{$h{$k}}];@_?&f:\%h
}

##</code><code>##

sub f {
  my@v;{$_=pop;/=>/||(push@v,$_)&&redo}
  $k=pop;$h{$k}=[@v,@{$h{$k}}];@_?&f:\%h
}