\NeedsTeXFormat{LaTeX2e} \ProvidesPackage{ifmtarg}[2018/04/16 v1.2b check for an empty argument] \begingroup \catcode`\Q=3 \long\gdef\@ifmtarg#1{\@xifmtarg#1QQ\@secondoftwo\@firstoftwo\@nil} \long\gdef\@xifmtarg#1#2Q#3#4#5\@nil{#4} \long\gdef\@ifnotmtarg#1{\@xifmtarg#1QQ\@firstofone\@gobble\@nil} \endgroup \endinput