Try putting the file name into another string, then printing that string to the STDERR log file.   Let the program tell you what it is doing.

my $debugging = 1;
my $filename = "$inddirect/company$qtr$yr.idx";
print STDERR "Opening '$filename'\n" if ($debugging);
open(INPUT, $filename) || die "can't open '$filename'";
print STDERR "'$filename' opened successfully\n" if ($debugging);
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