To see what is actually being passed to my_sub, you may want to try using Data::Dumper to see what @_ actually contains.

#!/usr/bin/perl -w

use Data::Dumper;
use strict;

my ($arg1,$arg2,$arg3) = qw(arg1 arg2 arg3);

my $ret_val = my_sub($arg1, "", $arg2, "", "", $arg3);

sub my_sub{
print Dumper(\@_);
my $arg1 = shift;
my $undef1 = shift;
my $arg2 = shift;
my $undef2 = shift;
my $undef3 = shift;
my $arg3 = shift;
....... and so on
}
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antirice    
The first rule of Perl club is - use Perl
The ith rule of Perl club is - follow rule i - 1 for i > 1