Hello, sorry I'm also still learning Perl/programming, and I have never used any WWW::Mechanize modules, but I'm curious, and after looking at the Instagram login page with firefox devtools I would suggest simulating more page interaction, like what happens if you 'click' the user name input field with:

$mech->click({xpath => '//input@name="username"', single => 1 });

then fill the input field value with:

$mech->value( username => $user );

then 'click' Log In.

I also want to say it looks to me like the Javascript 'events' are what is preventing a simple solution here, and by simple I suppose I mean something that seems obvious to someone like me who doesn't really know javascript. Hope that may help, sorry if it was just wasting time, but I am curious to see if that would at least make the label go away in the first picture/example :)