Like most of the other answers I will recommend Text::CSV but with a hopefully helpful explanation. Your question is asking for comma separated fields but a field can also contain a comma (,) enclosed in quotes ("). What about a field that needs to have " characters in it as well? CSV has a standard way of handling all these issues and it is not so easy to do with one regex. What about a,b,c,"",e,f ? Again CSV will just handle it. The use of List::Util suggested by swl makes a good refinement but hopefully the example below is a start: 
#!/usr/bin/env perl

use Modern::Perl;
use Text::CSV;

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

my @strings = (
    'a,"b,c",3,4,5,6',
    'a,"b,c",3,4,5',
    'a,"b,c",3,4,5,""',
    'abc,def,"ghi,jkl",,mno,6'
);

foreach my $s (@strings) {
    if (my $status = $csv->parse($s)) {
        if ( (grep { /\w/ } $csv->fields) != 6 ) {
            warn "row failed: ", $csv->string
        }
    }
    else {
        warn $csv->error_input
    }
}

[download]
Ron

In reply to Re: check if string is valid with special cases by mr_ron
in thread check if string is valid with special cases by ovedpo15

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