Regular expression for vim and emacs modelines.

modelines.rb

/
  (?:
    (-\*- \s* (?:mode:)? \s*) |                  # $1: Emacs
    (\/\* \s* vim: \s* set \s* (?:ft|filetype)=) # $2: Vim
  )
  (\w+)                                          # $3: language
  (?:
    (?(1)                                        # If $1 matched...
      ;?\s* -\*- |                               # then close Emacs syntax
      : \s* \*\/                                 # otherwise close Vim syntax
    )
  )
/x

samples.txt

; -*-php-*-
# ; -*- mode: php;-*-
# /* vim: set filetype=perl: */
# /* vim: set ft=perl: */