Bug 1: use strict; is missing. It'll show some encapsulation errors (i.e. a few missing mys).
Bug 2: use warnings; is missing. It'll show Bug 3.
Bug 3: func2 is declared after a call to it, so the prototype is ignored for that call.
Bug 4: You're using prototypes. Don't.
Bug 5: You modified $, without localizing it. (local $, = "...";)

use strict;
use warnings;

sub func1 {
  my $nums = shift;
  print("func1: ", join(', ', @$nums), "\n");
  func2($nums);
}

sub func2 {
  my $nums = shift;
  print("func2: ", join(', ', @$nums), "\n");
}

my @nums = (10,400,2,7,20,40,23,100,2);
print("main:  ", join(', ', @nums), "\n");
func1(\@nums);
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