The big performance killer is searching your entire set of drives twice.

Search through the drives once and pop the names on to 2 arrays. Then go and perform your modifications.

Also index is quicker than a regex.

Quick hack and untested:

my @rename_files;
my @modify_files;

finddepth (\&get_filenames , @fixedDrives );

sub get_filenames
{  
    push(@rename_files,$File::Find::name) 
       if( index($File::Find::name,$old_hostname) + 1 ); #index should
+ be quicker
    push(@modfy_files,$File::Find::name) 
       if ( -T $File::Find::name );  # -T is the same as -f and ! -B
                                                   
  }
[download]