Can't Perl detect which version is installed or something?

It's not about the perl version being installed. Once you invoke a perl binary, its version is fixed.

But modern perl versions also have the ability to act like older perls. For example 5.012 has strict implied if you declare that version, but it can also act like an older perl and be non-strict by default.

Now you could argue that the perl binary should autodetect the version of the script, but that's not possible in the general case. A script can be valid in different versions of perl, and produce different output (I've written such a script for educational purposes.

So it could only guess, but guessing is very dangerous. And since Perl cannot be parsed without executing it, autodetection could have dangerous side effects.

Perl 6 - second systems done right

In reply to Re: Why version strings? by moritz
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.