#!/usr/bin/perl
use warnings;
use strict;
use POSIX;
use Time::HiRes qw( ualarm );

### Detect if the mouse is moving or stopped. Tested on Raspian Linux.
### Adapted from http://www.the-ownage.com/?p=835
### The guy soldered a pair of wires to a mouse button 
### and used it to detect water leaks and send himself notifications.
my $fd;
my $buf;
my $mousedev="/dev/input/mouse0";

$fd = POSIX::open($mousedev, &POSIX::O_RDONLY) or die ("Cannot open $mousedev: $!");

my $stopped = 1;
print time,"--Mouse is stopped--\n";

while( 1 ) {
    local $SIG{ALRM} = 
        sub { 
            print time,"--Mouse is stopped--\n" if ! $stopped; #on transition
            $stopped = 1;    ### turn on output bit on Raspberry Pi
            $buf =""; 
        }; 
    ualarm 200_000;          ## time out after 0.2 seconds
    POSIX::read($fd, $buf, 1);
    if ( $buf and $stopped ) {
        print time,"--Mouse is moving--\n";     
        $stopped = 0;        ### turn off output
    }
    ualarm 0;
}