my @sorted=do{
    my $n;
    my %stuff=map { func($_) . ':' . $n++ => $_ } @unsrt;
    @stuff{sort keys %stuff};
};

##</code><code>##

my @sorted=do{
    my @keys=map func($unsrt[$_]) . ":$_", 0 .. $#unsrt;
    @unsrt[ map +(split /:/)[-1], sort @keys ];
};

##</code><code>##

my @sorted=@unsrt[ map +(split /:/)[-1],
    sort map func($unsrt[$_]) . ":$_", 0 .. $#unsrt ];

##</code><code>##

my @sorted=map $unsrt[ (split /:/)[-1] ],
  sort map func($unsrt[$_]) . ":$_", 0 .. $#unsrt;