use strict;
use warnings;

while (my $line = <DATA>) {
   if ($line =~ /CLI/) {
      chomp $line;
      while (my $line2 = <DATA>) {
         next unless $line2 =~ /\S/;  # ignore blank lines
         $line .= " $line2";
         last;
      }
   }
   print $line;
}

__END__
MVC   DOWO(8),WCPA   
                    
CLI   WCPA+2,C'.'  
                      
BNE   UPCC22