It's common to come across date strings in log files that you want to convert to a Unixtime. Perl has Data::Parse which offers a str2time() function to do this.

use Date::Parse;

my $ut = str2time("Thu, 13 Oct 94 10:13:13 +0700") # 782017993;

I wrote a version of strtotime() in a function that may be more portable. It has the limitation that it does not support timezone strings, but if you don't need them then it is a valid alternative.