Some digging around points to the rules file being at present available at http://anonscm.debian.org/cgit/collab-maint/nginx.git/tree/debian/rules

Since the package-specific configures appear to inherit via the $(common_configure_flags) statement, modifying only that block may suffice:

$ perl -00 -ple 's{$}{ \\\n\t\t\t--add-module=\$(MODULESDIR)/ngx_pagespeed} if m/common_configure_flags :=/' rules > nu $ diff -u rules nu --- rules 2015-12-17 14:49:12.000000000 -0800 +++ nu 2015-12-17 14:52:52.171942309 -0800 @@ -47,7 +47,8 @@ --with-http_ssl_module \ --with-http_stub_status_module \ --with-http_realip_module \ - --with-http_auth_request_module + --with-http_auth_request_module \ + --add-module=$(MODULESDIR)/ngx_pagespeed 

This solution treats the file contents in turns of paragraphs (-00 -p), and adds the necessary data at the end of each (and appropriate backwhacking, newline, and tabbery), but only for the paragraph that matches the common_configure_flags := bit. To target each section (instead of just the common one), one would need to fiddle around with the if regular expression as appropriate.

Some digging around points to the rules file being at present available here.

Since the package-specific configures appear to inherit via the $(common_configure_flags) statement, modifying only that block may suffice:

$ perl -00 -ple 's{$}{ \\\n\t\t\t--add-module=\$(MODULESDIR)/ngx_pagespeed} if m/common_configure_flags :=/' rules > nu $ diff -u rules nu --- rules 2015-12-17 14:49:12.000000000 -0800 +++ nu 2015-12-17 14:52:52.171942309 -0800 @@ -47,7 +47,8 @@ --with-http_ssl_module \ --with-http_stub_status_module \ --with-http_realip_module \ - --with-http_auth_request_module + --with-http_auth_request_module \ + --add-module=$(MODULESDIR)/ngx_pagespeed 

This solution treats the file contents in turns of paragraphs (-00 -p), and adds the necessary data at the end of each (and appropriate backwhacking, newline, and tabbery), but only for the paragraph that matches the common_configure_flags := bit. To target each section (instead of just the common one), one would need to fiddle around with the if regular expression as appropriate.