how to combine directory path in perl

I am having a perl script in which i am giving path to directory as input. Directory has xml files inside it.

In my code i am iterating through all the xml files and creating absolute path for all xml files. Code is working fine.

#!/usr/bin/perl

use File::Spec;

$num_args = $#ARGV + 1;
if ($num_args != 1) {
   print "\nUsage: $0 <input directory>\n";
   exit;
}

my $dirPath = $ARGV[0];

opendir(DIR, $dirPath);
my @docs = grep(/\.xml$/,readdir(DIR));

foreach my $file (@docs) 
{
   my $abs_path = join("",$dir,$file);

   print "absolute path is $abs_path";
}

Question i have here is, joining $dirPath and $file with no separator which means that $dirPath must end in a "/". So is there any way or built in function in perl which take cares of this condition and replaces the join method.

All i want is not to worry about the separator "/". Even if script is called with path as "/test/dir_to_process" or "/test/dir_to_process/", i should be able to produce the correct absolute path to all xml files present without worrying about the separator.

Let me know if anyone has any suggestions.