Cannot reproduce pkg-fallout failure

Since early this month (about two weeks after upgrading to 10.1.0.1) 
pkg-fallout has been complaining about net-mgmt/check_nwc_health for 
123amd64. However I cannot get the build to fail on my own 
12.3-RELEASE/amd64 poudriere build server.

The error comes from a subst script:

     /usr/bin/awk: illegal repetition expression: class ^#! ?\/.*\/[a-z]{0,2
      source line number 44 source file ./subst
      context is
             /^#! ?\/.*\/[a-z]{0,2}awk/ {sub(/^#! 
?\/.*\/[a-z]{0,2}awk/,"#! >>>  /usr/bin/awk") <<< ;}
     *** Error code 2

Line 44 looks (of the /usr/bin/awk shebang script) like this:

     /^#! ?\/.*\/[a-z]{0,2}awk/ {sub(/^#! ?\/.*\/[a-z]{0,2}awk/,"#! 
/usr/bin/awk");}

The port has no options. The differences between 10.0.0.2 and 10.1.0.1 
are small (~100 lines) and are limited to about half version number 
changes and half perl code changes; nothing related to assembling the 
script for installation has changed.

I thought maybe the regex was getting truncated but haven't been able to 
reproduce the error by shortening it. There are four places in 
"one-true-awk" that print this error and you have to do something to the 
bound specification like make it empty ({}), make n > m, double the 
comma, or include a character that's not a digit or comma.

Does anyone see the problem?

		Craig