Regular Expressions: low-caps, dots, zero spaces

[Quarum]

how do I write an expression which checks for lowcaps, dots, and without any white space in the string?the code below so far was trying to check for lowcaps and dots (it does not work anyway!) but I don't know how to add in the expression for white spaces.\[code\]# check for matches of lowcaps or lowcaps with a dotif (!preg_match('/([a-z0-9]|[a-z0-9\.])/', $cst_value)){ $error = true; echo ' please use lowcaps only with dot(s) and without any spacing.';}\[/code\]any ideas?many thanks,Lau