Well, I wouldn't call CPAN "adult content", I think it's at least (or is that "at most"?) PG-13 or even G-rated :-)

"mature", or "professional" are more appropriate words.

Anyway, to stay on topic, here my stab at it (of course, for irregular verbs, the Lingua::EN modules are better than List::MoreUtils):

#!/usr/bin/env perl
use 5.011; # implies strict
use warnings;
use List::MoreUtils 'pairwise'; # this is it

my @pronouns = qw(I thou he/she/it we you they);
my @endings = ('', 'st', 's', '', '', '');
print "predicate?\n";
my $predicate = <>;
my ($verb, $rest) = split ' ', $predicate, 2;
pairwise {
    no warnings 'once';
    print "$a $verb$b $rest"; # no \n because no chomp
} @pronouns, @endings;
[download]

A test with Input want a beer gives

I want a beer
thou wantst a beer
he/she/it wants a beer
we want a beer
you want a beer
they want a beer
[download]