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#!/usr/bin/perl

use strict;
use warnings;

use Carp::Clan qw(croak);
use File::Monitor;

my $filename = shift @ARGV;
my $duration = int(shift @ARGV || 5);

croak qq|No such file. ($filename)| unless (-e $filename);
croak qq|Invalid duration| unless ($duration >= 1);

my $monitor = File::Monitor->new;
$monitor->watch(
    $filename, 
    sub {
        my ($name, $event, $change) = @_;
        if ($change) {
            print "modified\n";
        }
    }
);

while (1) {
    $monitor->scan;
    sleep $duration;
}