I assume your ordered teachers are in an array @preferred, and your unsorted teachers are in @unsorted Then, 
my %order = do {my $i = 0; map {$_ => $i++} @preferred};
my @sorted;
$sorted[$order{$_}] = $_ for @unsorted;
@sorted = grep {defined} @sorted;

[download]
No sort() needed. Expected runtime: O(N), where N is the total number of teachers.

In reply to Re: Sorting based on a specific order by JavaFan
in thread Sorting based on a specific order by byteflow

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