G'day ovedpo15,

You can do your validation with this condition:

$string =~ y/,/,/ == -1 + grep length y/ //dr, split /,/, $string
[download]

I ran these tests based on the ever-shifting goal posts throughout this thread. :-)

$ alias perle
alias perle='perl -Mstrict -Mwarnings -Mautodie=:all -E'
$ perle 'my $x = "a,b,c"; say +($x =~ y/,/,/ == -1 + grep length y/ //
+dr, split /,/, $x) ? "Y" : "N"'
Y
$ perle 'my $x = "a,b ,c"; say +($x =~ y/,/,/ == -1 + grep length y/ /
+/dr, split /,/, $x) ? "Y" : "N"'
Y
$ perle 'my $x = "a,  ,c"; say +($x =~ y/,/,/ == -1 + grep length y/ /
+/dr, split /,/, $x) ? "Y" : "N"'
N
$ perle 'my $x = "a, ,c"; say +($x =~ y/,/,/ == -1 + grep length y/ //
+dr, split /,/, $x) ? "Y" : "N"'
N
$ perle 'my $x = "a,,c"; say +($x =~ y/,/,/ == -1 + grep length y/ //d
+r, split /,/, $x) ? "Y" : "N"'
N
[download]