#!/usr/bin/perl -w

use strict;
use warnings;

use Fcntl qw( :seek );
use IO::Handle;
use FileHandle;
use File::Find;

my $root = shift( @ARGV );
unless ( $root and ( -d $root)) {
    usage();
    exit( 1 );
}

my %args = (
     "wanted" => \&process,
     "no_chdir" => 1,
);

File::Find::find( \%args, $root );

exit( 0 );

sub process {
  my $path = $_;
  if ( $path !~ /htm?$/i) { return; }

   my $fh = new FileHandle( $path, "r+" );
   unless ( $fh ) {return;}

   my $data = join( "", $fh->getlines() );
  
  my $spat = 'gmx.de';
   
    my $rpat = 'yahoo.de';
  unless ( $data =~ s~$spat~$rpat~g) {
    $fh->close();
    return;
  }

   seek( $fh, 0, SEEK_SET );
   truncate( $fh, 0);
   $fh->print( $data);
   $fh->close();
}

sub usage {
   STDERR->print("usage: $0<root directory>\n" );
}