I don't know about the efficiency but here is how i would write it, (ignoring the CGI part).

use strict;
use warnings;

use Date::Calc qw(Delta_Days Decode_Date_US Today);

my $date1 = '1/1/2010'; # Supose date is in US format

my ( $year , $month , $day  ) = Today();
my ( $year1, $month1, $day1 ) = Decode_Date_US($date1);

my $dd = Delta_Days( $year1, $month1, $day1, $year, $month, $day );

print "There were $dd days between Today and $date1\n";
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