Take a look at some of the date modules, including Date::Calc or even Class::Date. An example of the latter would look like:

 use strict;
 use Class::Date;

 my ( $m, $d, $y ) = split( '/', '10/24/2000' );
 my $d = Class::Date->new([ $y, $m, $d ]);
 my $before = $d - '1D';
 print "Day before: $before";
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Chris
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