I know, this question was asked more than 7 years ago, but I would
like to post a sub that I wrote that does exactly what you want: 

sub CollapseWhitespace{@_ or return'';my$T=shift;defined$T
or return'';my$L=length($T);$L or return'';my$c;my$N=0;my$P
=0;my$U=1;for(my$i=0;$i<$L;$i++){$c=vec($T,$i,8);if($c<33){
$U=0;if($N++==1){vec($T,$P++,8)=32;}}else{$N=0;$U or vec($T
,$P,8)=$c;$P++;}}return$U?$T:substr($T,0,$P);}

[download]

^^ This looks a bit obfuscated, so here is a nicer expanded version: 


##############################################################
#
# This function removes single instances of whitespace and
# converts multiple adjacent whitespace characters to a single
# space. In this function, "whitespace" is defined as a character
# whose ASCII value is less than 33. (This includes many special
# characters such as new line characters, nul, bel, etc.)
#
#   Usage: STRING = CollapseWhitespace(STRING)
#
#   Example:
#     CollapseWhitespace("\n\t abc 123   xxx\n") --> " abc123 xxx"
#
sub CollapseWhitespace
{
  @_ or return '';
  my $T = shift;
  defined $T or return '';
  my $L = length($T);
  $L or return ''; 

  my $c;
  my $N = 0;    # consecutive whitespace counter
  my $P = 0;    # target pointer to overwrite original str $T
  my $U = 1;    # string length will be left unchanged
  for (my $i = 0; $i < $L; $i++)
  {
    $c = vec($T, $i, 8);
    if ($c < 33)
    {
      $U = 0;
      if ($N++ == 1) { vec($T, $P++, 8) = 32; }
    }
    else
    {
      $N = 0;
      $U or vec($T, $P, 8) = $c;
      $P++;
    }
  }
  return $U ? $T : substr($T, 0, $P);
}

[download]

In reply to Re: Removing extra spaces by harangzsolt33
in thread Removing extra spaces by rickoy

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