use strict;
use warnings;

while (my $line = <DATA>)
{      
   (my @words) = $line =~ /([^:.,\s]+)/g;
   # (my @words) = split /[:.,\s]+/, $line; #TRY THIS LINE INSTEAD
   next unless @words; # skip input lines that have no "words"
   
   print "\'$_\' " foreach @words;
   print "\n";
   
}

=prints:
Note: that the first data line with only ':' is skipped.
'this' 'is' 'a' 'simple' 'space' 'separated' 'line' 
'this' 'is' 'a' 'line' 'with' 'spaces' 'at' 'the' 'beginning' 
'this' 'line' 'has' 'multiple' 'spaces' 'embedded' 'in' 'it' 
'a' 'comma' 'list' 'a' 'b' 
'unconsidered' 'are' '(1)' 'item' 'lists' 'or' '(comments' 'like' 'this)' 
'$this_is_a_program_variable' 
'this' 'shows' '"a' 'quote"' 
=cut


__DATA__
:
this is a simple space separated line
     this is a line with spaces at the beginning
  this line has    multiple spaces embedded in     it
a comma: list,a,b
unconsidered are: (1) item lists  or (comments like this)
  $this_is_a_program_variable
this shows "a quote"