def _read_header_lines(lines, iline, line, log):
    """
    reads a tecplot header

    Examples
    --------
    **Example 1**

    TITLE     = "tecplot geometry and solution file"
    VARIABLES = "x"
    "y"
    "z"
    "rho"
    "u"
    "v"
    "w"
    "p"
    ZONE T=""processor 1""
    n=522437, e=1000503, ZONETYPE=FEBrick
    DATAPACKING=BLOCK

    **Example 2**

    title="Force and Momment Data for forces"
    variables="Iteration"
    "C_L","C_D","C_M_x","C_M_y","C_M_z""C_x","C_y","C_z","C_Lp","C_Dp", "C_Lv", "C_Dv""C_M_xp"
    "C_M_yp","C_M_zp","C_M_xv","C_M_yv""C_M_zv","C_xp","C_yp","C_zp","C_xv","C_yv""C_zv
    "Mass flow","<greek>r</greek>","u"
    "p/p<sub>0</sub>","T","p<sub>t</sub>/p<sub>0</sub>"
    "T<sub>t</sub>","Mach"
    "Simulation Time"
    zone,t="forces"
    """
    i = 0
    title_line = ''
    active_key = None
    vars_found = []
    header_lines = []
    while i < 30:
        if len(line) == 0 or line[0] == '#':
            line = lines[iline].strip()
            iline += 1
            i += 1
            continue
        if line[0].isdigit() or line[0] == '-':
            log.debug('breaking...')
            break
        uline = line.upper()
        uline2 = uline.replace(' ', '')
        if 'TITLE=' in uline2:
            title_line += line
            vars_found.append('TITLE')
            active_key = 'TITLE'
        elif 'VARIABLES' in uline2:
            vars_found.append('VARIABLES')
            active_key = 'VARIABLES'
        else:
            if 'ZONE' in uline2:
                vars_found.append('ZONE')
                active_key = 'ZONE'
            if 'ZONETYPE' in uline2:
                vars_found.append('ZONETYPE')
                active_key = 'ZONE'
            if 'DATAPACKING' in uline2:
                vars_found.append('DATAPACKING')
                active_key = 'ZONE'
        if active_key in ['ZONE', 'VARIABLES']:
            header_lines.append(line.strip())
        i += 1
        line = lines[iline].strip()
        iline += 1
    log.debug('vars_found = %s' % vars_found)
    return iline, title_line, header_lines, line
