In this example (from https://github.com/gisle/tkx/blob/2c96533/lib/Tkx.pm#L338), $) is highlighted as if it were an interpolated variable:
last if $pkg !~ /^Tkx(::|$)/;
Likewise $| would be highlighted in this equivalent statement:
last if $pkg !~ /^Tkx($|::)/;
However $ is highlighted correctly when using m// instead of //:
last if $pkg !~ m/^Tkx(::|$)/;
last if $pkg !~ m/^Tkx($|::)/;