use strict;
use warnings;

my $line_out;
open ( MOV, "<", "test.cxv" ) or die "test.csv: $!\n";

while (<MOV>) {
    if ( /^RS,/ ) {
        s/\s+$/,/;
        $line_out = $_;
    }
    elsif ( /^RAd,/ ) {
        s/\s+$/,/;
        $line_out .= $_;
    }
    elsif ( /^RC,/ ) {
        print $line_out . $_;
    }
}