#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my $aref;

print STDERR 'before: ' . Dumper($aref);
x($aref);
print STDERR 'after func: ' . Dumper($aref);
push (@{$aref},'hownow');
print STDERR 'last:' . Dumper($aref);

sub x{
        my $in = shift;
        push (@{$in},'whatever');
        print STDERR 'infunc:' . Dumper($in);
}

[download]

before: $VAR1 = undef;
infunc:$VAR1 = [
          'whatever'
        ];
after func: $VAR1 = undef;
last:$VAR1 = [
          'hownow'
        ];
[download]