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#!/usr/bin/perl
use strict;
...
close $infile;

print Dumper(\%students);

$VAR1 = {
          'Smith Tom' => {
...
                            'f4' => 'Fr'
                          }
        };

for my $student (sort {$students{$a}{id} <=> $students{$b}{id}} keys %
+students) {
    print "$student => $students{$student}{id}\n";
}