Another possible solution?

#!/usr/bin/perl

use strict;

my $file_1 = <<EOF;
Bbbb,3333,4444
Cdd,3444,3444
Zddd,345,456
EOF

my %records;
open( my $fh, "<", \$file_1 )
  or die "error opening file.";

while( <$fh> ) {
    chomp;
    my @cols = split( "," );
    $records{$cols[0]} = "$cols[1],$cols[2]";
}

close( $fh );

while (<DATA>) {
    my @cols = split( "," );
    $cols[0] =~ s/_\w+//;
    print "$cols[0],$records{$cols[0]},$cols[1],$cols[2]";
}
__DATA__
Bbbb_rf1,23,45
Cdd_rf2,24,45
Zddd,34,456.4
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