You can use Time::Piece, a core module. The formats can be found on the man page for strptime.
use Time::Piece;
my $tp = Time::Piece->strptime("23.10.2011 11:35:00",
"%d.%m.%Y %H:%M:%S");
print $tp->epoch; # 1319369700
print $tp; # "Sun Oct 23 11:35:00 2011", same as $tp->cdate