$ cat shabba
for my $key ( grep /perl/i , keys %ENV ){ print qq{ $key $ENV{$key}\n}; }

$ perl shabba
 PERL_MB_OPT  --config installhtmldir=  --binhtml=

$ perl -e " $ENV{PERL_SHABBA}=666; system $^X, q{shabba}; "
 PERL_SHABBA 666
 PERL_MB_OPT  --config installhtmldir=  --binhtml=  --config installhtmldir=  --binhtml=

$ perl shabba
 PERL_MB_OPT  --config installhtmldir=  --binhtml=