The comma operator can be complicated.
I would not use the comma operator in this complex of a situation.

If there are multiple parts, put () around the comma parts(eg (part1), (part2,)) and it will parse like you expect.

#!usr/bin/perl -w
use strict;

for my $i (1..9)
{
  (print "Next"), 
   next if $i == 5;
   print $i
}

__END__
Output:
1234Next6789
[download]

Another what I think is better coding (don't use the comma if not needed):

#!usr/bin/perl -w
use strict;

for my $i (1..9)
{
  if ($i == 5)
  {
     print "Next";
     next;
  }
  print $i;

}

__END__
Output:
1234Next6789
[download]

The basic thing with the comma operator, is that what appears in the last part of the comma statement is what matters.