use warnings;
use strict;

while (my $line = <DATA>) 
{
  
   chomp $line;
   print "Input Line: '$line'\n";
   $line =~ s/(\S)-/$1 -/g;  # add space before minus if needed
                             # otherwise don't add a space
   print "Modified Line: '$line'\n";
   my @numbers = split ' ', $line;
   print "Numbers are @numbers\n\n";
}

=prints:

Input Line: '1.234 5.6789 -1.235-4'
Modified Line: '1.234 5.6789 -1.235 -4'
Numbers are 1.234 5.6789 -1.235 -4

Input Line: '1.234 5.6789-12.235-4'
Modified Line: '1.234 5.6789 -12.235 -4'
Numbers are 1.234 5.6789 -12.235 -4

=cut


__DATA__
1.234 5.6789 -1.235-4
1.234 5.6789-12.235-4