But what happens if the GPA is equal for a bunch of students and you want those students listed in alphabetic order? Your sort needs to be more advanced.

use strict;
use warnings;

my %students = (
    0354 => "Fred\t3.2",
    4873 => "Tom\t2.9",
    4874 => "Bill\t2.9",
    1522 => "Susan\t4.0",
);

$_ = [split /\t/, $_] for values %students;

print "$students{$_}[0] (#$_} $students{$_}[1]\n" for
    sort { $students{$b}[1] <=> $students{$a}[1] ||
           $students{$a}[0] cmp $students{$b}[0] }
    keys %students;
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