#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11145633
use warnings;
use List::AllUtils qw( nsort_by );

my @weekdays = qw/Monday Saturday Thursday/;

print "$_\n" for
  nsort_by { 'motuwethfrsasu' =~ substr lc, 0, 2; $-[0] } @weekdays;
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Outputs:

Monday
Thursday
Saturday
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