How do you usually figure the code for a hash traversal?

Not sure what you’re asking here, but for the record, the line:

print $g->{files}->{$file}->{raw_url};
[download]

can be simplified to:

print $g->{files}{$file}{raw_url};
[download]

because “The arrow is optional between brackets subscripts” (perlref#Using-References, point 3).

Do you usually use the debugger and inspect the hash?

No, I’d likely use Data::Dump or Data::Dumper, as in the OP.

Anyway, glad the problem has been sorted. :-)