# Keep the lookup table in highest scope necessary to avoid create/destroy each time needed
my %lookup = ( Jan => 0, Feb => 1, ... );

#Assume unpack is faster than regex (Benchmark.pm to be sure)
# Add code to handle year appropriately
my ($mon, $day, $hr, $min, $sec) = unpack('A3xA2xA2xA2xA2', $date);
$mon = $lookup{$mon};
my $stamp = timelocal( ... );