use warnings;
use strict;

my $line = "word 15,000 word word 20,000";
my @line = split /\s+/, $line;
my $sum;
foreach my $word (@line) {
   next unless $word =~ /^[\d,.+-]+$/; # crappy number detector
   $word =~ s/,//g;
   $sum += $word;
}
print "$sum\n";