in reply to Re: Why version strings?
in thread Why version strings?

Also note that use v5.10; == use 5.10.0; == 5.010;. But use 5.10; == use 5.100;. Which, IMO, is not very DWIM.

An unfortunate side-effect of having two similar but very different numbering systems. At least the error message is useful. 

$ perl -e'use 5.10;'
Perl v5.100.0 required (did you mean v5.10.0?)--this is only v5.12.2, 
+stopped at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

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I don't know whether there's a (single-line) syntax that at compile time checks for 5.10, but which doesn't enable features. 

$ perl -M5.014 -e1
Perl v5.14.0 required--this is only v5.12.2, stopped.
BEGIN failed--compilation aborted.

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Re^3: Why version strings?
by JavaFan (Canon) on Mar 29, 2011 at 09:13 UTC 
    $ perl -M5.014 -e1
Perl v5.14.0 required--this is only v5.12.2, stopped.
BEGIN failed--compilation aborted.

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    I fail to understand how that answers my question:
    I don't know whether there's a (single-line) syntax that at compile time checks for 5.10, but which doesn't enable features.
    If I substitute 5.010 for 5.014, 5.10 features are enabled: 
    $ perl -M5.010 -e 'say "foo"'
foo

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      You can use require for version checks, but a better solution is to put it in the installation script.
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        You can use require for version checks
        That delays the version check to run-time, resulting in unwanted compilation errors: 
        $ perl-5.8.8 -e 'require 5.010; /1++/'
Nested quantifiers in regex; marked by <-- HERE in m/1++ <-- HERE / at
+ -e line 1.

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        as opposed to 
        $ perl-5.8.8 -e 'use 5.010; /1++/'
Perl v5.10.0 required--this is only v5.8.8, stopped at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

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        but a better solution is to put it in the installation script.
        That would be an argument against the entire use 5.XXX; syntax; it also assumes there's only one Perl version on the system - and it will never change. Not to mention many scripts don't come with an installation script. (For instance, most complete programs posted on Perlmonks are presented as-is, without an installation script).
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