while(<DATA>) {
    chomp;
    my ($k, $v) = split / \s+ \d+ , \s+ /x;
    print "key: $k ... value: $v$/";
    # or stuff it in a hash:
    $hash{$k} = $v;
}

__DATA__
73     63, galileo measur us newton basi law motion
75     45, galileo experi bodi roll slope act same forc weight effect make constantli speed up
70     50, show real effect forc chang speed bodi set move previous thought
75     50, meant bodi act forc keep move straight line same speed
65     45, idea first state explicitli newton principia mathematica publish 1687 known newton first law
75     50, happen bodi forc act given newton second law