#!/usr/bin/perl
use 5.016;
# 1030798ALT

my $str = "chapter 1,2,3";     # out: "chapter 1,chapter  2,chapter 3"
my ($chapter, @num);

if ( $str =~ /^(chapter) / ) {
	$chapter = $1;
	# say "\$chapter: |$chapter|";
}

my @chapnums = ( $str =~ /(\d[,]*)/gc);
	if ( @chapnums) {
		push @num,@chapnums;
	}

for my $num(@num) { 
	# say "DEBUG   \$#num: $#num";
	# if ( $1 != (1 + $#num) ) {
	# 	print "\$chapter $num" . ",";
	# } elsif ( $1 == (1 + $#num) ){
	print "$chapter $num";
}