I'm a little late to this party but I would take either of two approaches using regular expressions. The middle initial is optional and occurs at the end of the string so you can match that with (?:\s[A-Z]\.?)?\z and either discard it via substitution or capture a non-greedy match of everything up to it. Like this

use strict;
use warnings;

my @names = (
   q{Mark K.},
   q{Bob H},
   q{Kurt},
   q{Mary Kay K},
   q{Mary Jo Z.},
   q{Mary Jo});

print
   qq{Original    Substituted Matched\n},
   qq{--------    ----------- -------\n};
foreach my $name (@names)
{
    (my $firstNameBySubs = $name) =~ s{(?:\s[A-Z]\.?)?\z}{};
    my ($firstNameByMatch) = $name =~ m{^(.*?)(?:\s[A-Z]\.?)?\z};
    printf qq{%-12s%-12s%-s\n}
       , $name
       , $firstNameBySubs
       , $firstNameByMatch;
}
[download]

This produces

Original    Substituted Matched
--------    ----------- -------
Mark K.     Mark        Mark
Bob H       Bob         Bob
Kurt        Kurt        Kurt
Mary Kay K  Mary Kay    Mary Kay
Mary Jo Z.  Mary Jo     Mary Jo
Mary Jo     Mary Jo     Mary Jo
[download]

Cheers,

JohnGG