Perl Inotify not responding to append (ie, echo 'test' >> file) - perl

Question

When running the below test code to watch a file, events are only detected if I do a 'vim' on the file and write it out (or write-quit). Doing an 'echo' to the file, or adding text via perl is not detected.
test_inotify.pl:
#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;
use Carp;
use IO::File;
use Linux::Inotify2;
$|++;
my $readfile = shift;
#my $action = "IN_CLOSE_WAIT";
#my $action = "IN_MODIFY";
#my $action = "IN_OPEN";
my $action = "IN_ALL_EVENTS";
unless ($readfile) { $readfile = "test.txt" };
my $inotify = Linux::Inotify2->new();
$inotify->watch($readfile, $action)
or die "Inotify watch on " . $readfile . "failed: $!\n";
while () {
my #events = $inotify->read();
unless (#events > 0) {
print "Inotify Read Error: $!\n";
exit;
};
foreach my $event (#events) {
print "Detected Event: " . $event->fullname . "\n";
};
};
test_fh_write.pl:
#!/usr/bin/perl -w
use strict;
use warnings;
use diagnostics;
use Carp;
use IO::File;
$|++;
my $readfile = shift;
unless ($readfile) { $readfile = "test.txt" };
my $readfh = IO::File->new( $readfile, ">>" ) or
#my $readfh = IO::File->new( $readfile, ">" ) or
die "Cannot open $readfile: $!";
$readfh->autoflush(1);
if ($readfh) {
print $readfh "test\n\n";
};
undef($readfh);
I've tried with test_fh_write.pl as well as echo commands like this: 'echo a >> test.txt', 'echo "test" >> test.txt', etc.
I have also tried with the "$|" character and without (even with $fh->autoflush(1)), but to no avail. Each of the $action variables defined in test_inotify.pl I've tried, but they all result the same.

Answer 1

I think the second argument to Linux::Inotify2::watch is a number/bitmask, not a string. You should be calling
$inotify->watch($readfile, IN_ALL_EVENTS)
instead of
$inotify->watch($readfile, "IN_ALL_EVENTS")
The bareword IN_ALL_EVENTS is resolved to the (presumably constant) function &Linux::Inotify2::IN_ALL_EVENTS.