• Your code is not strict/warnings compliant, you should fix those first.
• use eq for string comparison, not ==.
• say already adds a newline, maybe stick to print ? :)
• use any::feature 'say';
• For examples, stuff your example data into __DATA__ aka __END__

That all adds up to

#!/usr/bin/perl --

use strict;
use warnings;

use any::feature 'say';

while (<DATA>)
{
    my @line = split(/ /,$_);
    say $line[2] if  $line[2] eq '<stuff>';
}
__END__
Date Time <stuff> 3344 123456789
Date Time could be good
Date Time <otherstuff> 4321
Date Time <sohappy> this is really great
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