And another alternative is to use open:

my $result;
# first open or die
open my $eject, '-|', 'eject -n' or die "Can't eject: $!\n";
# Then read in lineby line
while (<$eject>) {
    next unless /^device is/;
    # until the result is found
    $result= $_;
    last;
}
# done
close $eject;
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Especially when filtering output, I prefer this method because you can loop over the output line by line and react as soon as you found your searched input.