That's interesting and very clear. And it led me straight to the solution for my particular case about Class::DBI on the different machines. Both have version 3.0.17 of Class::DBI, but on Linux #1:

[mcdave@maia ~perl -MClass::DBI -MClass::ISA -e 'foreach $f (Class::IS
+A::super_path("Class::DBI")) { print join(" ", $f, ${"${f}::VERSION"}
+, "\n" ) ;}'
Class::DBI::__::Base -1, set by base.pm 
Class::Accessor 0.34 
Class::Data::Inheritable 0.08 
Ima::DBI 0.35 
[mcdave@maia ~]$ perl -MClass::DBI -e 'print Class::DBI->can("import")
+ ? "yes" : "no", "\n"'
yes
[download]

but on Linux #2:

[mcdave@trowel ~]$ perl -MClass::DBI -MClass::ISA -e 'foreach $f (Clas
+s::ISA::super_path("Class::DBI")) { print join(" ", $f, ${"${f}::VERS
+ION"}, "\n" ) ;}'
Class::DBI::__::Base -1, set by base.pm 
Class::Accessor 0.33 
Class::Data::Inheritable 0.08 
Ima::DBI 0.35 
[mcdave@trowel ~]$  perl -MClass::DBI -e 'if( Class::DBI->can("import"
+) ) { print "yes" } else { print "no" }; print "\n"'
no
[download]

So I conclude that the "difference" is in Class::Accessor!

Thanks for your clear explanation