Added  __DATA__

#!/usr/bin/perl
use warnings;
use 5.16.2;

$/ = "\n+";
while (<DATA>) {
    if ($_ =~ m/\+/) {
            s/\n\+//;
    }
    print;
}
say '';

__DATA__
xabcd a1
+b1
+b2
+b3
+b4
+b5 abcd
xcdef c1
+d1
+d2
+d3
+d4
+cdef
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