use Data::Dumper;
use strict;

my @arr;

while (<DATA>) {
    s/\s+$//;
    push @arr, [split /\s+/, $_] if $_;
}

print Dumper(\@arr);

@arr = sort {
    $b->[2] <=> $a->[2]
} @arr;

print Dumper(\@arr);

__DATA__
A BBL 0.2

B BBH  0.3

C BB 0.1