UNIX for Dummies Questions & Answers

$ cat infile
This is a book
The book is on the shelf and the pen is on the table
$ cat script.pl
use strict;
use warnings;

my %word = map { $_ => 1 } qw/the and a/;

while ( <> ) {
        chomp;
        my @f = split;
        for my $pos ( 0 .. $#f ) {
                if ( exists $word{ lc $f[ $pos ] } ) {
                        my $last_word = $pos + 5;
                        printf qq[%s %s\n], ucfirst $f[ $pos ], join qq[ ], @f[ $pos + 1 .. ($last_word > $#f ? $#f : $last_word) ]; 
                }
        }
}
$ perl script.pl infile
A book
The book is on the shelf
The shelf and the pen is
And the pen is on the
The pen is on the table
The table