As an general practice, I do not fiddle around with $1 and $2. I use list context to assign these variables to specific names. This avoids some complications and is not "expensive" in terms of CPU..

use strict;
use warnings;

while (<DATA>) 
{
  if ( (my $first,my $second) = /^([^ ]+) ([^ ]+)/ )
  {
      print "$first $second\n";
  }
}  

#prints: hello one

__DATA__
hello one two three
kjsf
kjsd
kjd
[download]

Now of course the regex could be written differently. This means the same thing.

use strict;
use warnings;

while (<DATA>) 
{
  if ( (my $first,my $second) = /^(\S+)\s+(\S+)/ ) #ok, allow an extra
+ spaces between tokens
  {
      print "$first $second\n";
  }
}  

#prints: hello one

__DATA__
hello one two three
kjsf
kjsd
kjd
[download]