here is the part of the bowtie wrapper script , i need to get accession for the source code of following files which are made bold in the below script. I am trying to modify the script for my needs but i am unable to get source code.

($vol,$script_path,$prog) 
                = File::Spec->splitpath($prog);
my $os_is_nix   = $^O ne "MSWin32";
my $align_bin_s = $os_is_nix ? **'bowtie2-align-s'** : 'bowtie2-align-s.exe'; 
my $build_bin   = $os_is_nix ? **'bowtie2-build'** : 'bowtie2-build.exe';               
my $align_bin_l = $os_is_nix ? **'bowtie2-align-l'** : 'bowtie2-align-l.exe'; 
my $align_prog_s= File::Spec->catpath($vol,$script_path,$align_bin_s);
my $align_prog_l= File::Spec->catpath($vol,$script_path,$align_bin_l);
my $align_prog  = $align_prog_s;
my $idx_ext_l     = 'bt2l'; 
my $idx_ext_s     = 'bt2'; 
my $idx_ext       = $idx_ext_s; 
my %signo       = ();
my @signame     = ();