A simple recurring alarm clock written in Perl (does not require any packages, just plain perl). This version is specific to Windows but could easily be converted to other platforms.

alarmclock.pl

#!/usr/bin/env perl
#
# a (very simple) recurring alarm clock for windows
# easily converted to any other platform by replacing the call to the windows msg tool
# all data is stored in the file itself (in the __DATA__ section at the bottom)
# this is written in pure perl, no packages are required
#
# under windows I suggest using the ActiveState wperl interpreter to launch the alarm clock
# that prevents you from having a command processor hanging around just to run the alarm clock
# the unfortunate side effect is that you have to kill it using task manager since it never exits
#

#
# Copyright (c) 2019 by James Brown
#
# This software is released into the public domain
# Do with it what you will (please don't use it for evil)
# Don't blame me if it doesn't work for you
#



########################
# config section
########################
$pause = 10;	# time to display the message, in seconds

$debug = 0;		# set to non-zero for verbose debug info

########################
# end config
########################



$dataStart = tell DATA; # save the original position

while(1)
{
	($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime;
	warn "Running at $hour:$min:$sec on day $wday\n" if ($debug);

	seek DATA, $dataStart, 0;	# position to start of data section
	
	while(<DATA>)
	{
		chomp;
		s/\r|\n//g;
		
		warn "DATA: $_\n" if ($debug);

		next if (/^\s*[;#]/);	# comment lines can start with pound or semi-colon
		
		# optionally match either a w or W or any string of digits, with or without commas
		# then a time
		# then a message
		if (/^\s*(?:([wW]|(?:\d+?(?:,\d)*,?))\s+)?(\d{1,2}):(\d{1,2})\s+(.+)/)
		{
			$d = $1;
			$h = $2;
			$m = $3;
			$msg = $4;
			
			$d='0,1,2,3,4,5,6' if ($d eq '');	# blank = daily
			$d='1,2,3,4,5' if ($d eq 'W');		# weekdays, Mon-Fri
			$d='0,6' if ($d eq 'w'); 			# weekend, Sat, Sun
			
			warn "day string: $d\n";
			
			`msg \%USERNAME\% /time:$pause "$msg"` if ($h == $hour && $m == $min && $d =~ /$wday/);
		}
	}
	
	warn "sleeping ...\n" if ($debug);
	sleep(60 - (time() % 60));	# sleep until the next minute
}


###########################################
# in the DATA section (below), put in all your alarms
# times in 24 hour format
#
# the format of each line is
# [d] hh:mm message
#
# the optional first parameter (d) is the day(s) the alarm should be active
#    this can be one or more day numbers (0=Sunday, 1=Monday, etc.) seperated by commas (but no spaces)
#    or it can be 'w' for weekend (Sat, Sun) or 'W' for weekdays (Mon-Fri)
#        (mnemonic is 'w' is shorter than 'W' because weekends are shorter than the work week)
#    leaving the day parameter off means every day (daily alarm)
#
# some examples
# -------------
# W 7:15 Time to wake up (on weekdays)
# w 9:00 Time to wake up (on weekends)
# 1,3,5 12:00 Team lunch (on Mon, Wed, Fri)
# 18:30 Dinner time! (daily)
#

__DATA__