Setting $/ to undef is good, but it won't exactly what the person asked for, namely, concatenate a space between each record. Only the join ' ', <> idiom will do that.

Be that as it may, I think using <> in array context is going to build up a huge AV temporary (Perl's internal representation of an array). Also, I have a sneaking suspicion the person would also like to get rid of the newlines of each record, in which case one would do something like:

  my $foo;
  while( <> ) {
    chomp; # maybe, maybe not, depending on the circumstances
    if( defined( $foo )) {
      $foo .= " $_";
    }
    else {
      $foo = $_;
    }
  }
[download]

--

g r i n d e r