Perl evolves, and sometimes this manifests itself in incompatible changes. Those are documented in the various perldelta documents.

The Perl 5 porters try to keep those changes minimal, and often they only affect relatively seldom used constructs.

Perl 6 - links to (nearly) everything that is Perl 6.

In reply to Re: Script validity between different perl versions by moritz
in thread Script validity between different perl versions by targetsmart

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