Oddity in Params::ValidationCompiler

validate.pl

use strict;
use warnings;

use Types::Standard qw/Int Str/;
use Params::ValidationCompiler qw( validation_for );

sub foo {
  my ($num) = validation_for(
    params => [
      { type => Str }
    ]
  )->(@_);

  print $num;
}

foo(1);