txt2para.pl

#!/usr/bin/env perl

# Turn consecutive non-empty lines of plain text into paragraphs

local $/ = "\n\n";    #paragraph separator

while (<>) {
  chomp($_);

  # Replace newlines inside paragraphs by spaces and remove multiple spaces
  s/\n/ /g;
  s/ +/ /g;

  # Print each non-blank block out separated by the paragraph separator
  print "$_\n\n" if (!(/^\s*$/));

}