Perl doesnt find some modules

i am using Version 18.06.00 on my archer c7. Perl ist installed under:
@inc points to 5.28. ( perl -e "print "@inc"")
Some modules are missing, for example, because it resides only under 5.26.

I few days ago all were fine, because all perl stuff was installed under 5.26. Now some things resides in 5.26, others in 5.28.
This cannot work ..., i think
Is there a trick ?
regards Klaus