Since 5.12, use 5.012; could also introduce changes in behaviour. I'm not too fond of that

Since 5.10, actually. If there was no change in behaviour, there wouldn't be need for the features pragma at all. 

$ perl -e'sub say { print "foo\n"; }  say for "bar";'
foo

$ perl -E'sub say { print "foo\n"; }  say for "bar";'
bar

[download]

It was always safe to try

It's no more or less safe to try now as then. By switching use 5.008; for use 5.006;, you could get bugs that changed behaviour and compile-time errors just like you do now.

Update: Deleted a comment based on something I misread.

In reply to Re^2: Why version strings? by ikegami
in thread Why version strings? by gunzip

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.