+ 15 => array(# style of drawing
+ 'dashed','drawoptions','pickup','withcmykcolor','withcolor',
+ 'withgreyscale','withpen','withpostscript','withprescript',
+ 'withrgbcolor','curl','tension'
+ ),
+ 16 => array(# read write show
+ 'errhelp','errmessage','fontmapfile','fontmapline','interim',
+ 'loggingall', 'message','scantokens','show','showdependencies',
+ 'showtoken','showvariable','tracingall','tracingnone','write to'
+ ),
+ 17 => array(# Internal variables with numeric values
+ 'ahangle','ahlength','bboxmargin','charcode','day','defaultcolormodel',
+ 'defaultpen','defaultscale','dotlabeldiam','hour','labeloffset',
+ 'linecap','linejoin','minute','miterlimit','month','mpprocset',
+ 'pausing','prologues','restoreclipcolor','showstopping','time',
+ 'tracingcapsules','tracingchoices','tracingcommands','tracingequations',
+ 'tracinglostchars','tracingmacros','tracingonline','tracingoutput',
+ 'tracingrestores','tracingspecs','tracingstats','tracingtitles',
+ 'troffmode','truecorners','warningcheck','year'
+ ),
+ 18 => array(# Internal string variables
+ 'filenametemplate','jobname','outputformat','outputtemplate'
+ ),
+ 19 => array(# other predefined variables
+ 'background','currentpen','currentpicture','cuttings','defaultfont',
+ 'extra_beginfig','extra_endfig'