Syntastic is a syntax checking plugin that runs files through external syntax
checkers and displays any resulting errors to the user. This can be done on
demand, or automatically as files are saved. If syntax errors are detected, the
user is notified and is happy because they didn't have to compile their code or
execute their script to find them.

At the time of this writing, syntax checking plugins exist for applescript,
c, coffee, cpp, css, cucumber, cuda, docbk, erlang, eruby, fortran,
go, haml, haskell, html, javascript, json, less, lua, matlab,
perl, php, puppet, python, rst, ruby, sass/scss, sh, tcl, tex, vala, xhtml,
xml, xslt, yaml, zpt.