Looks like the useraccount IUSR_srvname doesn't know anything about the domain and can't find your domain controller automatically...

Try one of the following:

my $ad_server  = Win32::OLE->GetObject ("LDAP://servername")
  or die $!;
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or

my $adpath = "LDAP://$server/DC=my,DC=domain,DC=edu";
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or perhaps use GC: instead of LDAP: (GC is Global Catalog)