my $string = "";
   while ( <$IN> )                    ## $IN needs to be open
   {   chomp;
       if ( $_ eq "END" )
       {   $string = join ( " ", split " ", $string );
           # $string =~ s/$other//g;   ## In case you need to remove other characters
           print $OUT "$string\n";    ## $OUT is open output file
           $string = ""; next;
       }
       $string .= $_;
   }