Your question is a bit unclear, but for convenience I assume you want to subtract the two times in a line.

You would think you could use the Date::Manip module, but that's only so if you don't need sub-second precision. Date::Manip handles dates that are a whole number of seconds only, and will silently discard the microsecond part of your dates when parsing them. If this is okay with you, something like this works.

use Date::Manip::Date; 
my $d = Date::Manip::Date->new("2011-11-21 12:50:31.550"); 
my $e = $d->new("2011-11-21 08:49:16.000"); 
my $i = $e->calc($d); 
print $i->printf("%hys hours\n");
[download]

Update 2012-01-07: apparently this doesn't answer all you're asking: you also want to find the minimal time difference for each pair of location and team. I'm lazy to write an answer now.