use strict;
my $str = 'The client requires photos of a radioactive world
Reach the target planet.
The client requires photos.

Reach the target planet.
The client requires photos of a desert world
Reach the target planet.
The client requires photos of an airless world. Reach the target planet.
The client requires photos of a strange world

Reach the target planet
Make a quick scan.';
my $regex = qr/[^
\n]+/mp;
my $subst = '';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html