s `@load` a valid Perl keyword? Remember the lexer is still Perl. I didn't look at its code, but it almost certainly does not use the wordchars list for deciding whats a legal keyword, at least most lexers don't let Geany set that.
It's crazy, I know, but I was hoping that `geany` would allow customisation of things like `wordchars` and `keywords`. If only there was some feature like a configuration file for each file extension that allowed that.