use 5.010;
use strict;
use warnings; 

my $x = 23;
my $y;

debug({x => $x, y => $y});

sub debug {
    my ($d) = @_;
    my $s = join ' ', map { sprintf("$_='%s'", ($d->{$_} // '')) } sort keys %$d;
    say $s;
}