I have fixed the bug.
Thank you for the report.
[Patch]
RCS file: /sources/global/global/gtags.vim,v
retrieving revision 1.31
diff -r1.31 gtags.vim
3,4c3,4
< " Version: 0.6.4
< " Last Modified: Nov 24, 2012
---
> " Version: 0.6.5
> " Last Modified: Oct 21, 2013
276c276
< if a:line =~ '^Gtags'
---
> if a:line =~# '^Gtags'
296c296
< if l:c == 'e'
---
> if l:c ==# 'e'
338c338
< if l:c !~ '[cenpquv]'
---
> if l:c !~# '[cenpquv]'
355c355
< if a:option =~ 'f'
---
> if a:option =~# 'f'
387c387
< if l:option =~ 'f'
---
> if l:option =~# 'f'
389c389
< elseif l:option =~ 'P'
---
> elseif l:option =~# 'P'
391c391
< elseif l:option =~ 'g'
---
> elseif l:option =~# 'g'
433c433
< if l:option =~ 'f'
---
> if l:option =~# 'f'
481c481
< if s:option == 'g'
---
> if s:option ==# 'g'
483c483
< elseif s:option == 'f'
---
> elseif s:option ==# 'f'