I would tend to use substr rather than reverse to abbreviate the first name in this case:

#!/usr/bin/env perl

use warnings;
use strict;

while (<DATA>) {
    my ($last, $first) = split /,/;
    $last  =~ s/\s+//;
    $first =~ s/\s+//;
    print substr($first, 0, 1), $last, "\n";
}

__DATA__
Smith, John
Bar, Foo
[download]

Prints out:

JSmith
FBar
[download]