Thelonius, for some reason that "not space" at the end of your regex seems weird to me.

I like this solution, because it's an easy way to rule out lines that contain something (ie, "vet") anywhere after the first word, which is I think what the OP really wants to do.

while (<DATA>) {
    # match the first word
    # in lines that don't contain "vet" anywhere
    push(@array, $1) if m/^(?!\w+\b.*vet)(\w+)/i;
}

print("@array\n");

__DATA__
David    Veterinarian
Jackie  Orthopedist
Karen Veterinarian
Vetch   Orthopedist
Vetch   Veterinarian
[download]