use Cwd;
$dir = cwd();
 
$vardas=$dir;
 
while($vardas=~/(.*\/)+(.*)/){
 
$vardas="$2_source";
}
 
$newfile = "$dir/$vardas.tex";
 
FILE: foreach $file (<@ARGV>) {
  if ($file eq $newfile) {next FILE};
 if (-e "$dir/$vardas.tex"){
   print "File exist\n";}
else{
print "Rename: "."$file\n";
 
  rename ($file, $newfile) || die "Can't rename.\n";}
 
}

 
while($vardas=~/(.*\/)+(.*)/){
     $vardas="$2_source";
}