Jaheuk
for me, "commax" indicates you are probably suffering a code-page issue in NLS (national language support) with the square brackets on zOS.
I don't recall clearly but in SAS6 days (where I got most of my more-recent
😉 experience of zOS-SAS) there was a work-around with iirc !( and !) or something like that. (in the last millennium!! the zOS keyboards I worked on did not support square brackets so SAS provided those alternatives.
At
http://support.sas.com/documentation/cdl/en/lrdict/63026/HTML/default/viewer.htm#a000205506.htm the CHARCODE system option is documented describing how characters required by syntax but not on a "keyboard", can be achieved with a ?-combination.
I was wrong about ?( and ?) That documentation shows it should be ?< and ?>
good luck
peterC