Fix #400 (perl lexer mishighlights $x=shift)
Fix #400 (perl lexer mishighlights $x=shift)

spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments