$
$ ## the awk script, for the 4th field instead of the 19th
$ echo "abc,def,456,the good bad ugly,xyz" |awk -F, '{print $4}' |awk '{ for (i=2 ; i<=NF ; i++) print $1,$i}'
the good
the bad
the ugly
$
$

$
$ ## the Perl script
$ echo "abc,def,456,the good bad ugly,xyz" | perl -F, -lane '@x=split/ /,$F[3]; for($i=1; $i<=$#x; $i++){print "$x[0] $x[$i]"}'
the good
the bad
the ugly
$
$

this is a test

this, is a test

$
$
$ echo "1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,this is a test,20" | perl -pe 's/(([^,]*,){18}\w+)/$1,/'
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,this, is a test,20
$
$