Ooh, I just love the smell of homework.

First thing you need to do is read input lines using <>, not read. As in:

$time = <>;   chomp $time;
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You should probably do better matching of the specified $time against the values in the .dat file. E.g.

while (<$fh>)
{
   chomp;
   my( $n, $i, $t ) = split;
   $found = 1 if $t eq $time;
}
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But where is $studentNumber coming from?