[Perl syntax] Symbol "#" parsed as comment in regular expressions

[asy]

String from "#" is highlighted as comments:

$C =~ tr/!*?+\\\[\]#(){}=,:/.............../;

[baryluk]

Yes, that is tricky. JavaScript? also has similar issues with regexp interacting with a comment on a same line. #2145

I think the perl one like above should be fixable tho.