In my version of strftime, negative month day is ok, so the fix is easy: just subtract the week day from the month day:

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use POSIX qw( locale_h strftime );
setlocale( LC_TIME, 'fr_FR' );

my @date = localtime;
$date[3] -= $date[6];

my @wd = map {
    $date[3]++;
    strftime '%A', @date
} 0 .. 6;
print "@wd\n";
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Note that a single array element is written $date[6], without the at-sign.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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