use Text::CSV_XS;

my $csv = Text::CSV_XS->new;

while(<DATA>){
    chomp;
    my @columns = split /\t/;

    $csv->combine( @columns ) or die "could not combine due to ",$csv->error_input()," in input\n";

    print $csv->string, "\n";
}

__DATA__
first   second
"hello" 100,000
bye He said "bye"

##</code><code>##

first,second
"""hello""","100,000"
bye,"He said ""bye"""

##</code><code>##

first,second
"hello",100,000
bye,He said "bye"