while(<DATA>){
    chomp;
    next unless length;
    say "$_ => [", (m/(\d*\.?+\d*)/x ? "$1]" : ']');
}

__DATA__
0.12
.12
12.
12

##</code><code>##

0.12 => [0.12]
.12 => [.12]
12. => [12.]
12 => [12]

##</code><code>##

m/( \d*  \.?+  \d* )/x    # Mine
m/( \d*  \.?   \d+ )/x    # Yours