use 5.010;
given( $number ) {
    when( /\D/ )
        { say "\thas nondigits"; continue }
    when( /^\d+\z/ )
        { say "\tis a whole number"; continue }
    when( /^-?\d+\z/ )
        { say "\tis an integer"; continue }
    when( /^[+-]?\d+\z/ )
        { say "\tis a +/- integer"; continue }
    when( /^-?(?:\d+\.?|\.\d)\d*\z/ )
        { say "\tis a real number"; continue }
    when( /^[+-]?(?=\.?\d)\d*\.?\d*(?:e[+-]?\d+)?\z/i)
        { say "\tis a C float" }
}