You already have some good answers, but here is another that just reverses your search (ie instead of searching for a-zA-Z it searches for anything that is not a-zA-Z and negates the answer):

$temp2 !~ m/[^a-zA-Z]/
[download]

This will return false if it finds a character that is not a-z or A-Z. The [^ ] only matches if none of the characters contained in the brackets are found.

You could reverse your condition to make the code easier to read with this method:

if ($temp2 =~ m/[^a-zA-Z]/)
{
 die "Wrong input";
}
else
{
 $naam = $1;
}
[download]

- Cees