#! perl -slw
use strict;

# assuming the name of the compound file is supplied on the command line

until( eof( ARGV ) ) {
    my @buffer = <>;                                   ## Put the <DOCUMENT> tag into a clean buffer
    push @buffer, scalar( <> ), scalar( <> );          ## Ditto <TYPE> & <SEQUENCE>
    my( $filename ) = ( my $line = <> ) =~ m[<FILENAME>(\S+)];
    push @buffer, $line;

    open OUT, '>', $filename or die $!;
    print OUT for @buffer;
    print OUT until ( $_ = <> ) =~ m[</DOCUMENT>];
    close OUT;
}