use strict;
use warnings;
use Data::Dumper;

my %UnNum = (
    "forc two bodi twice strong on bodi sai bodi mass"  => 35,
    "you expect on think new bodi made two bodi origin" => 39,
    "attract bodi b origin force"                       => 60,
    "total forc b twice origin force"                   => 46,
    "sai on bodi twice mass three time mass forc six"   => 34,
    "on now see why bodi fall same rate bodi twice"     => 17 );
my @midWords = qw/bodi forc twice mass acceler law/;
    
my $joined = join("|", @midWords);
my $regex = qr/\b$joined\b/;
print Dumper(\%UnNum);
for my $sentence (keys %UnNum) {
    $UnNum{$sentence}++ while $sentence =~ /$regex/g;
}
print Dumper(\%UnNum);