# find duplicate words in paragraphs, possibly spanning line boundaries.
#   Use /x for space and comments, /i to match the both `is' 
#   in "Is is this ok?", and use /g to find all dups.
$/ = '';        # paragrep mode
while (<>) {
    while ( m{
		\b            # start at a word boundary
		(\S+)         # find a text chunk
		( 
		    \s+       # separated by some whitespace
		    \1        # and that chunk again
		) +           # repeat ad lib
		\b            # until another word boundary
	     }xig
	 ) 
    {
	print "dup word `$1' at paragraph $.\n";
    } 
}