Two solutions:

use Algorithm::Loops qw( NextPermute );

sub mysort {
   my @a = @_;
   1 while NextPermute(@a);
   return @a;
}

my @unsorted = qw( a c b d );
my @sorted = mysort(@unsorted);
print("@sorted\n");
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use IPC::Run3 qw( run3 );

sub mysort {
   my @unsorted = map "$_\n", @_;
   run3([ 'sort' ], [ map "$_\n", @unsorted ], \my @sorted);
   chomp(@sorted);
   return @sorted;
}

my @unsorted = qw( a c b d );
my @sorted = mysort(@unsorted);
print("@sorted\n");
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