# first, generate fixed-precision strings for magnitudes
# and bin values:

my @mag_keys = map { sprintf("%.1f", $_/10) } ( 50 .. 89 );
my @bins = qw/0 0.1 0.3 1 3 10 30 1000/;

# now initialize hash bins for counting:
# (this is probably unnecessary, unless you're re-using
# the hash on multiple separate data sets)

my %n;
for my $mag ( @mag_keys ) {
    for my $bin ( @bins ) {
        $n{$mag}{$bin} = 0;
    }
}