using System;
    using System.Text.RegularExpressions;
     
    public class Test
    {
    public static void Main()
    {
    var testString = "BP -1.23e4 5.67";
     
    var mspaces = @"\s+"; // meaning as many spaces as you want
    var cdouble = @"([+\-]?(?:0|[1-9]\d*)(?:\.?\d*)(?:[eE][+\-]?\d+)?)"; // meaning capture a double
     
    var shortPattern = String.Join("", "BP", mspaces, cdouble, mspaces, cdouble);
    var longPattern = String.Join("", "BP", mspaces, cdouble, mspaces, cdouble, mspaces, cdouble, mspaces, cdouble);
     
    var bpShort = Regex.Match(testString, shortPattern, RegexOptions.IgnoreCase);
    var bpLong = Regex.Match(testString, longPattern, RegexOptions.IgnoreCase);
     
    if (bpLong.Success)
    {
    Console.WriteLine("Long pattern detected"); // !!FALSE-MATCH!!
    }
    if (bpShort.Success)
    {
    Console.WriteLine("Short pattern detected");
    }
    }
    }