gistfile1.txt

#!/usr/bin/env perl

use strict;
use warnings;

use Date::Manip::Date;

my($command_date_string, @command) = @ARGV;

my $command_date = Date::Manip::Date->new;
$command_date->parse($command_date_string);

my $command_time = $command_date->secs_since_1970_GMT;
my $sleep_time = $command_time - time;

if( $sleep_time >= 0 ) {
    print $command_date->printf("The command will run at %C.\n");
}
else {
    print "The command will run right now.\n";
}

if( !fork ) {
    sleep $sleep_time if $sleep_time > 0;
    exec @command;
}