given ($year_anchor_day){
    when(0){@anchorday_week = qw(tuesday wednesday thursday friday sat
+urday
    sunday monday );}
    when(1){@anchorday_week = qw(wednesday thursday friday saturday su
+nday
    monday tuesday);}
    when(2){@anchorday_week=qw(thursday friday saturday sunday monday 
+tuesday
    wednesday);}
    when(3){@anchorday_week=qw(friday saturday sunday monday tuesday w
+ednesday
    thursday);}
    when(4){@anchorday_week=qw(saturday sunday monday tuesday wednesda
+y
    thursday friday);}
    when(5){@anchorday_week=qw(sunday sunday monday tuesday wednesday 
+friday
    saturday);}
    when(6){@anchorday_week = qw(monday tuesday wednesday thursday fri
+day
    saturday sunday);}
}

[download]
This looks ugly to me, and it's not the programmer's task to repeat the same information multiple times. 
@anchorday_week = qw(tuesday wednesday thursday friday saturday sunday
+ monday);
my @tmp = splice @anchorday_week, 0, $year_anchor_day;
push @anchorday_week, @tmp;

[download]
(see splice). Probably there are more elegant solutions, but at least it is shorter and won't warn you about given/when …

Update: even simpler: drop that complete @anchorday_week, and then change the calculation of your $nbdays to 

my $nbdays = ($diff_to_doomsdates + $year_anchor_day) % 7;
return qw(tuesday wednesday thursday friday saturday sunday monday)[$n
+bdays];

[download]

In reply to Re: Doomsday algorithm by soonix
in thread Doomsday algorithm by QuillMeantTen

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