Alarm is useful if you want to remind yourself to check for the files in two minutes, but do something else in the meanwhile. It's also good for timing out blocking system calls.

Frankly I don't see how it can be useful here, unless you do something like

$SIG{ALRM} = 'IGNORE';
alarm 120;
sleep; # forever, or until interrupted
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Which is, IMHO, a redundant and less reliable way to get the same effect as

sleep 120;
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