try

while( <DATA> ) {
  my @matches = /(\w+)/g;
  print join( ',', @matches ), "\n";
}
[download]

or

while ( <DATA> ) {
  while ( /(\w+)/g ) {
    print $1, "\n";
  }
}
[download]

also, you're missing a semicolon after the regexp, but I assume that you just typed that out, and didn't cut and paste =)