docbook2X depends on perl5.26, but seems to require perl5.28

[szhorvat (Szabolcs Horvát)]

The docbook2X port depends on perl5.26:

port info docbook2X
docbook2X @0.8.8_10 (textproc)
Variants:             universal

Description:          Converts DocBook documents into the traditional Unix man
                      page format and the GNU Texinfo format.
Homepage:             http://docbook2x.sourceforge.net/

Library Dependencies: perl5.26, p5.26-xml-namespacesupport, p5.26-xml-sax,
                      p5.26-xml-parser, p5.26-xml-sax-expat, libiconv, libxml2
Conflicts with:       docbook-utils
Platforms:            darwin
License:              MIT
Maintainers:          Email: tlockhart1976@gmail.com, GitHub: lockhart
                      Policy: openmaintainer

But it appears to require perl5.28:

~ $ db2x_xsltproc
Failed to execute process '/opt/local/bin/db2x_xsltproc'. Reason:
The file '/opt/local/bin/db2x_xsltproc' specified the interpreter '/opt/local/bin/perl5.28', which is not an executable command.

The db2x_xsltproc script has this at the beginning:

#!/opt/local/bin/perl5.28

[jmroot (Joshua Root)]

This port needs to specify which perl version to use. Because it doesn't, it uses whichever version perl5 currently points to, which can be different between the build machine and the end user's.

[szhorvat (Szabolcs Horvát)]

Related: ​https://trac.macports.org/ticket/58361

[dbevans (David B. Evans)]

In 3af940b09b9ad5b13516972bb6d45d53f1d63bc4/macports-ports (master):

docbook2X: add perl variants, rebuild

• set default_branch to 5.28
• add size to checksums

See #58361.
Fixes #60423.

[dbevans (David B. Evans)]

In fb5328f7b3ab33b4f4325774f0ca5c8fe11c2fb3/macports-ports (master):

other ports with perl variants: explicitly set +perl5_28 as default

Protects against the default variant being unexpectedly changed to
port perl5's active variant. This could result in the run time default
being different from the build time default with fatal consequences.

For an example, see #60423.