A combination of Week_Number, Monday_of_Week, and Add_Delta_Days should do it:

use warnings;
use strict;

use Date::Calc qw( Week_Number Monday_of_Week Add_Delta_Days );

my ( $year, $month, $day ) =  ( 2003, 8, 9 );

my $week = Week_Number ( $year, $month, $day );
( $year, $month, $day ) = Monday_of_Week ( $week, $year );

print "", join(" ", Add_Delta_Days ( $year, $month, $day, $_ )), "\n"
    foreach 0..6;
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