my $BMinus = substr ($B, 0, (index ($B,&CheckFile(\$A,$B)) - 1));

sub CheckFile {
	my ($P_ref,$T) = @_;
	&CrawlForward($P_ref,\$T);
	while (!(-s "$$P_ref\\$T") || (-s $T)) {
		$$P_ref =~ s/\A(.+)\\[^\\]+\z/$1/;
		&CrawlForward($P_ref,\$T);
	}
	return $T;
}
sub CrawlForward {
	my ($C_ref,$T_ref) = @_;
	my $FHold = $$T_ref;
	while (!-s "$$C_ref\\$$T_ref") {
		unless ($$T_ref =~ s/\A[^\\]+\\(.+)\z/$1/) {
			$$T_ref = $FHold;
			last;
		}
	}
	return 1;
}