Assuming your file association is correct
Windows 7 Enterprise with Perl 5_16 from active state

C:\Users\utillitarian>type test.pl
#!/usr/bin/perl
$dir=$ARGV[0];
use Data::Dumper;
print Dumper(\@ARGV);
print "$dir\n";
print shift;

C:\Users\utillitarian>perl test.pl foo
$VAR1 = [
          'foo'
        ];
foo
foo
C:\Users\utillitarian>
[download]

Perl's file association is to gvim on this box though