$ perldoc -f chown
  ($login,$pass,$uid,$gid) = getpwnam($user)
    or die "$user not in passwd file";

##</code><code>##

$ perl --version
This is perl, v5.8.5 built for i386-linux-thread-multi
$ uname -a
Linux hopalong 2.6.9-42.0.10.EL #1 Tue Feb 27 09:24:42 EST 2007 i686 i686 i386 GNU/Linux
$ perl -wle 'use strict; my (undef,undef,$uid,$gid) = getpwnam(q[roo]) || die "oh no"; print $uid;'
Use of uninitialized value in print at -e line 1.

$ perl -wle 'use strict; my (undef,undef,$uid,$gid) = getpwnam(q[roo]) or die "oh no"; print $uid;'
500