I can't read joerg's thoughts better than yourself, but I debug
slightly differently than you:
# make show-var VARNAME=DEPENDS
{perl>=5.6.0,p5-PathTools>=0.80}:../../devel/p5-PathTools
perl>=5.14.0:../../lang/perl5 perl<5.16.0:../../lang/perl5
# make show-var VARNAME=BUILD_DEPENDS
{perl>=5.7.3,p5-Test-Simple>=0.47}:../../devel/p5-Test-Simple
{perl>=5.6.0,p5-ExtUtils-MakeMaker>=0.30}:../../devel/p5-ExtUtils-MakeMaker
The DEPENDS show that this package already needs perl>=5.14, so the
BUILD_DEPENDS' pattern of {perl>=5.7.3,something else} will always be
fulfilled by perl and the rest of it is ignored. At least that's how I
think it's generally supposed to work.
No idea what tinderbox does differently here, but I guess it just
takes the path after the colon.
Thomas