+my $cplex= "
+Maximize
+
+ totalprofit:
+ ".(join " +
+ ", map { "$_->{profit} $_->{Var}" } @flows)."
+
+Subject To
+";
+
+my %avail_csts;
+foreach my $flow (@flows) {
+ foreach my $od (qw(org dst)) {
+ my $cstname= join '_',
+ 'avail',
+ $flow->{'commodid'},
+ $od,
+ $flow->{"${od}_id"},
+ $flow->{"${od}_price"};
+ push @{ $avail_csts{$cstname}{Flows} }, $flow->{Var};
+ $avail_csts{$cstname}{Qty}= $flow->{"${od}_qty"};
+ }
+}
+foreach my $cstname (sort keys %avail_csts) {
+ my $c= $avail_csts{$cstname};
+ $cplex .= "
+ ". sprintf("%-30s","$cstname:")." ".
+ join("+", @{ $c->{Flows} }).
+ " <= ".$c->{Qty}."\n";
+}
+
+$cplex.= "
+Bounds
+ ".(join "
+ ", map { "$_->{Var} >= 0" } @flows)."
+
+End
+";
+# glpsol --cpxlp /dev/stdin <t.cplex -o /dev/stdout
+