I doubt it's a good idea, since you might still want to pass more positional parameters. Otherwise you could just pass a list func(a=>1) with sub func { my %args = @_}

But for completeness a solution with the new refaliasing feature

use strict;
use warnings;
use Data::Dump qw/pp dd/;

use feature qw/refaliasing/;
no warnings "experimental::refaliasing";


sub tst {
    (\my %args) = @_;
    pp \%args;
}

tst({a=>1,b=>2});
[download]

C:/Perl_524/bin\perl.exe  d:/tmp/pm/refaliasing.pl 
{ a => 1, b => 2 }
[download]