Just for good measure, you could always use the DateTime distribution, something like

use DateTime::Duration;

my $toTime = "1220";
my $fromTime = "0930";

my $to = DateTime::Duration->new(
    hours   => substr($toTime,0,2),
    minutes => substr($toTime,2,2),
);

printf "%02d%02d\n", $to->hours,$to->minutes;

my $from = DateTime::Duration->new(
    hours   => substr($fromTime,0,2),
    minutes => substr($fromTime,2,2),
);

printf "%02d%02d\n", $from->hours,$from->minutes;

$to->subtract_duration( $from );
# $to = $to - $from ;
printf "%02d%02d\n", $to->hours,$to->minutes;
print
    $to->hours,
    " hours and ",
    $to->minutes,
    " minutes\n";


use DateTime;
$to = DateTime->now;
$to->set(hour   => substr($toTime,0,2) );
$to->set(minute => substr($toTime,2,2) );

print $to->strftime('%A, %B %d, %Y @ %H%M'),"\n";

print
$to->subtract(hours   => substr($fromTime,0,2) )
   ->subtract(minutes => substr($fromTime,2,2) )
   ->strftime('%A, %B %d, %Y @ %H%M'),"\n";

__END__
1220
0930
0250
2 hours and 50 minutes
Monday, September 08, 2003 @ 1220
Monday, September 08, 2003 @ 0250
[download]

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"

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