Is this supposed to be a UNC? a relative directory? You might take a look at using File::Spec to build your path to make sure that the directory seperators are correct. Something like
$path=File::Spec->catfile('//server','share','dir-1','*inst.tar.gz');
You might need to play around with this some to get it to work right. You might also want to chdir to the directory prior to running the glob.