Was this meant as an example to illustrate questions about how to work with globs or are you simply trying to pass a value into a function doublevalue(...)? The sample you have posted looks like a very old Perl coding style - what version of Perl are you working with?

If the point was to pass values, the current way to pass values is to use variables and references, like this:

use strict;
use warnings;
use Data::Dumper;
{
    my @arra = (10,20);

    #no need for & and you can just pass a reference
    #&doublevalue(*arra);
    doublevalue(\@arra); 
}

sub doublevalue {
  #my is preferred to local
  #local *a = shift ;
  my $a = shift;
  print Dumper @$a;
}
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If you want to learn more about how type globs work, see perlref.

Best, beth