use File::Find;

find (\&doSomething,'.'); # Find stuff in curr dir, execute subroutine do something on match.  (\&[name] is a subroutine pointer... )
exit(0); # not needed
sub doSomething{
  my $fn = $_; # also not needed but makes life easy
  if ((!(-d $fn)) && ($fn =~/tar$/i)){ # -d test not really necessary
    system("tar","-xvf",$fn); # May want to do a which tar if it doesn't work ...
  }
}