Just to explain the required change:

\&function returns a reference to function function. Temp::Tool->new is not a function — it's a Perl expression — so \& can't be used. sub { ... } creates an (anonymous) function and returns a reference to it. All you have to do is to create a small function which executes your Perl expression.

That trick can be used even if you have arguments, thanks to closures. For example,

my $func;

{
   my  $arg1 = 'Hello';
   $func = sub {
      my ($arg2) = @_;
      print("$arg1 $arg2\n");
   }
}

{
   my $arg1 = 'Goodbye';
   $func->('World');
}
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prints

Hello World
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Lexical (my) variables are captured when sub is executed, and arguments can still be passed in as a normal function.