#!/usr/bin/perl -w
use strict;

my @compounds=("C3H8O2",
	       "C6H10O5",
	       "C36H62O31",
	       "C5H16N2",
	       "C10H11N5O6P",
	       "C9H11N3O7P",
	       "C3H9N2O2");
print join("\n",
	   sort{  my ($num_A)  = ($a =~  /^C(\d+)/);           
		  my ($num_B)  = ($b =~  /^C(\d+)/);
		       $num_A <=> $num_B
		} 
	   grep { /P$/ } #could be just /P/?
	   @compounds),"\n";

__END__
C9H11N3O7P
C10H11N5O6P