Register? perldoc -f alarm

 eval {
     local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
     alarm $timeout;
     $nread = sysread SOCKET, $buffer, $size;
     alarm 0;
 };
 if ($@) {
     die unless $@ eq "alarm\n";   # propagate unexpected errors
     # timed out
 }
 else {
     # didn't
 }
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