
sub makeIndex {
    my ($swissFile) = @_;
    
    open my $sFH, '<', $swissFile or die "Cannot open file $swissFile";
    
    my $btPrev = 0;
    my %index;
    while ( my $line = <$sFH> ) {
	my $bt = tell $sFH;
	if ( $line =~ /^ID\s+(\w+)\s+/ ) {
	    $index{$1} = $btPrev;
	}
	$btPrev = $bt;
    }
    close $sFH;
    return \%index;

} # End of makeIndex

