please note you can also use qr//x to make the sub-terms more readable

> I was surprised that I had to escape the slashes

Well Quote-like-Operators can chose the delimiter freely.

like qr~~ or qr{}

> I used your suggestions

Well ... mainly AI suggestions ;-)

Some were good, others not to my taste.

TIMTOWTDI ...

Here my take

{ 
    my $HEX    = qr/ [0-9A-F]  /xi;
    my $HEX_X  = qr/ [0-9A-FX] /xi;

    my $H_opt  = qr/ [h]?      /xi;

    my $INT    = qr/ \b INT \s? $HEX{2} [hH]? /x;   # is longer $H_opt
+ better ???


    our $hyperlinkpattern = qr~
      ...
      $INT
      ...
    ~x;
}
[download]

Please note how the helper variables are restricted to the scope and how $HEX{2} is NOT interpreted as a hash-lookup (surprised me!).

Hope my suggestions helped you having better maintainable code :-)

There are many more improvements which come to mind but I'm prone to over-engineering and it's in you're in a better position to decide what works best for you =)