The [noun] [past_tense_verb] the [noun].
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#!/usr/local/bin/perl -w
use strict;

die "usage: $0 <madlib>" unless @ARGV;
my @story = <>;

# Set up the Text::Template normally.
use Text::Template;
my $t = new Text::Template(TYPE => 'ARRAY', SOURCE => [ @story ],
    DELIMITERS => ['[', ']']);

# compile the template; usually you don't need to
# call this, cause it gets called automatically.
# but we need to do some magic on its results.
$t->compile;

# This is magical. :)
# Mark-Jason Dominus probably wouldn't like me
# messing with the insides of his module. This
# extracts all of the template variables and
# creates closures for each, then sticks
# all of that into a hash.
my %hash = map { $_->[1], mk_subref($_->[1]) }
           grep $_->[0] eq "PROG",
           @{$t->{SOURCE}};

# Now we fill in the story, and we're done:
# we hand Text::Template the hash we've
# constructed. Each time it finds one of the
# template variables (in the template itself),
# it (magically) calls the closure we associated
# with it, which prompts the user and returns
# the word he/she entered; which is then filled
# into the template.
my $story = $t->fill_in(HASH => \%hash);
print $story;

# Returns a closure that prompts the user for a part
# of speech, then returns the word he/she enters
sub mk_subref {
    my $part = shift;
    return sub {
        print "Give me a $part: ";
        my $word = <STDIN>;
        chomp $word;
        $word;
    };
}
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