$ cat 1042506.pl
#!/usr/bin/env perl

use strict;
use threads;
use Thread::Queue;

my $q=Thread::Queue->new;
my $progref;

my $thr=async {
	$progref=$q->dequeue; #This seems to create a local $progref, but it shouldn't!
	print "In main part of thread \$progref=$progref\n";
	$$progref=30; #This is applied
	ch(); #This is ignored 
};

my $prog :shared;
$q->enqueue(\$prog);
sleep 2;
print "$prog\n"; #Prints 30, not 90
$q->end;
$thr->join;

sub ch {
    print "In ch \$progref=$progref\n"; #progref is still undefined (why?)
    $$progref=90;
}

$ perl 1042506.pl
In main part of thread $progref=SCALAR(0x84bfa60)
In ch $progref=SCALAR(0x84bfa60)
90