devel/imake-4 has a USE_PERL5 dependency, causing it to install Perl if
it's not already present.  It includes a script, mkhtmlindex, which
is written in Perl, and starts:

    #!/usr/bin/perl

This will fail if the following conditions are met:

  1.  The system was installed without selecting Perl in sysinstall.

  2.  Perl was subsequently installed from ports/packages (perhaps
      automatically by devel/imake-4 to satisfy its dependencies).

  3.  "use.perl port" hasn't been run.

In this case, /usr/bin/perl doesn't exist, and mkhtmlindex fails.

A lot of X11 ports then fail to completely install.  However, enough if
the installation completes that subsequent dependency checks often succeed,
so there's no attempt to reinstall them.  This leaves the package database
in an inconsistent state.

Fix: 

Patch mkhtmlindex so the shebang line is either:

    #!/usr/local/bin/perl

or

    #!/usr/bin/env perl
How-To-Repeat: 
Do steps 1, 2, and 3 above.