This one resulted in all kinds of trouble, like infinite loops :D This works like a charm on the other hand.

sub search_dir {

my ($dir) = @_;
print "Entered search_dir sub, working with directory => $dir \n";
my $dh; # handle

    if ( !opendir ($dh, $dir)) {
        warn "Unable to open $dir: $!\n";
        return;
    }
   
my @FILES = grep { $_ ne '.' && $_ ne '..' } readdir($dh);
    
foreach my $file (@FILES) {
    my $path = "$dir/$file";    
        if ( -d $path ) {
            print "Directory $path found\n";
            search_dir ($path); 
        }
        else {
            print "File $path found\n";
        }
}
closedir ($dh);
}
# END of search_dir sub

##############
Output:
...
File /csvfiles/2015/12/22.csv found
Directory /csvfiles/2015/10 found
Entered search_dir sub, working with directory => /csvfiles/2015/10 
File /csvfiles/2015/10/16.csv found
File /csvfiles/2015/10/22.csv found
Directory /csvfiles/2015/11 found
Entered search_dir sub, working with directory => /csvfiles/2015/11 
File /csvfiles/2015/11/16.csv found
File /csvfiles/2015/11/11.csv found
...
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