RegExp {1} just ONE match

[adelante]

RegExp:

1. U1234
2. u12345
3. UuUuu1234
4. U123rGyA424

I want to make a thing that only matches number 1 and 2 kinds of strings, and keep 3, 4 and any other strings out. Here is my best try what am I doing wrong??

if ($string =~ /u{1}\d+(?![^.])/i) {
print "It's working!";
}

So, ONE 'u' or 'U' and then a number of any length - and only that.

The u{1} doesn't seem to be working for me.

Thanks

 

[TonyGroves]

How about:
[tt]
/^[uU]\d+$/
[/tt]

 

[adelante]

Wow, so simple...

Thanks alot!!!