手持ちのExuberant Ctagsが対応している言語を調べるだけの裏技っぽい何か

正攻法なら「--list-languages」を使う。

D:\temp>ctags --list-languages
Asm
Asp
Awk
Basic
BETA
C
C++
C#
Cobol
Eiffel
Erlang
Fortran
HTML
Java
JavaScript
Lisp
Lua
Make
Pascal
Perl
PHP
Python
REXX
Ruby
Scheme
Sh
SLang
SML
SQL
Tcl
Vera
Verilog
Vim
YACC

D:\temp>

裏技っぽくしたいなら「--verbose」を使う。「Installing parsers」で表示される言語が、手持ちのctagsで対応している言語になるはず。

D:\temp>ctags --verbose
Installing parsers: Asm, Asp, Awk, Basic, BETA, C, C++, C#, Cobol, Eiffel, Erlan
g, Fortran, HTML, Java, JavaScript, Lisp, Lua, Make, Pascal, Perl, PHP, Python,
REXX, Ruby, Scheme, Sh, SLang, SML, SQL, Tcl, Vera, Verilog, Vim, YACC
Setting option defaults
    Setting default header extensions: h, H, hh, hpp, hxx, h++, inc, def
  Installing default language mappings:
    Asm: (*.A51) (*.29[kK]) (*.[68][68][kKsSxX]) (*.[xX][68][68]) .asm .ASM .s .S
    Asp: .asp .asa
    Awk: .awk .gawk .mawk
    Basic: .bas .bi .bb .pb
    BETA: .bet
    C: .c
    C++: .c++ .cc .cp .cpp .cxx .h .h++ .hh .hp .hpp .hxx
    C#: .cs
    Cobol: .cbl .cob .CBL .COB
    Eiffel: .e
    Erlang: .erl .ERL .hrl .HRL
    Fortran: .f .for .ftn .f77 .f90 .f95
    HTML: .htm .html
    Java: .java
    JavaScript: .js
    Lisp: .cl .clisp .el .l .lisp .lsp .ml
    Lua: .lua
    Make: ([Mm]akefile) .mak .mk
    Pascal: .p .pas
    Perl: .pl .pm .plx .perl
    PHP: .php .php3 .phtml
    Python: .py .pyx .pxd .scons
    REXX: .cmd .rexx .rx
    Ruby: .rb .ruby
    Scheme: .SCM .SM .sch .scheme .scm .sm
    Sh: .sh .SH .bsh .bash .ksh .zsh
    SLang: .sl
    SML: .sml .sig
    SQL: .sql
    Tcl: .tcl .tk .wish .itcl
    Vera: .vr .vri .vrh
    Verilog: .v
    Vim: .vim
    YACC: .y
  Installing default exclude patterns:
    adding exclude pattern: {arch}
    adding exclude pattern: .arch-ids
    adding exclude pattern: .arch-inventory
    adding exclude pattern: autom4te.cache
    adding exclude pattern: BitKeeper
    adding exclude pattern: .bzr
    adding exclude pattern: .bzrignore
    adding exclude pattern: CVS
    adding exclude pattern: .cvsignore
    adding exclude pattern: _darcs
    adding exclude pattern: .deps
    adding exclude pattern: EIFGEN
    adding exclude pattern: .git
    adding exclude pattern: .hg
    adding exclude pattern: PENDING
    adding exclude pattern: RCS
    adding exclude pattern: RESYNC
    adding exclude pattern: SCCS
    adding exclude pattern: .svn
Considering option file /ctags.cnf: not found
Considering option file /etc/ctags.conf: not found
Considering option file /usr/local/etc/ctags.conf: not found
Considering option file D:\home\.ctags: reading...
  Option: --regex-javascript=/^[ \t]*(.*)[ \t]*:[ \t]*function/\1/m,methods/
Considering option file D:\home\ctags.cnf: not found
Considering option file .\.ctags: not found
Considering option file .\ctags.cnf: not found
Reading initial options from command line
ctags: No files specified. Try "ctags --help".

D:\temp>

ただそれだけ。特に意味はない。