#! perl
use strict;
use warnings;

my $file = '';

while (<DATA>)
{
    s{\\\n}{};
    $file .= $_;
}

print $file;

__DATA__
first line
second line \
third line \
fourth line
fifth line

##</code><code>##

13:10 >perl 738a_SoPW.pl
first line
second line third line fourth line
fifth line

13:13 >