Are you sure you really want a hash?

If you use the first two numbers digits as keys to a hash, then you will wind up with duplicate keys, and some of your data will be lost.

Of course this may be what you want. But if not, perhaps what you really want is a LoL

Update 1: the following code shows you the difference between putting your data into a hash, or a LoL (List of Lists)..

Update 2: actually, that's not a LoL at all - it's just a straight list. If we change the @LOL assignment to read:

push @LoL, [$key, $value];
[download]

then we get a LoL :)
I confused myself because I initially thought you wanted to separate all the words on each line. But anyway, I'm sure you get the idea :)

#!/usr/bin/perl -wl
use strict;
use Data::Dumper::Simple;

my %hash;
my @LoL;

while (<DATA>) {
    chomp;
    my ($key, undef, $value) = split /\s+/, $_, 3;
    $hash{$key} = $value;

    push @LoL, $key, $value;
}

print Dumper(%hash);
print Dumper(@LoL);

__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 th
+ought
75     50, meant bodi act forc keep move straight line same speed
65     45, idea first state explicitli newton principia mathematica pu
+blish 1687 known newton first law
75     50, happen bodi forc act given newton second law
[download]

Output:

%hash = (
          '70' => 'show real effect forc chang speed bodi set move pre
+vious thought',
          '75' => 'happen bodi forc act given newton second law',
          '73' => 'galileo measur us newton basi law motion',
          '65' => 'idea first state explicitli newton principia mathem
+atica publish 1687 known newton first law'
        );

@LoL = (
         '73',
         'galileo measur us newton basi law motion',
         '75',
         'galileo experi bodi roll slope act same forc weight effect m
+ake constantli speed up',
         '70',
         'show real effect forc chang speed bodi set move previous tho
+ught',
         '75',
         'meant bodi act forc keep move straight line same speed',
         '65',
         'idea first state explicitli newton principia mathematica pub
+lish 1687 known newton first law',
         '75',
         'happen bodi forc act given newton second law'
       );
[download]

Cheers,
Darren :)