Some info first:
$ perl -v | head -2 | tail -1
This is perl 5, version 18, subversion 2 (v5.18.2) built for x86_64-li
$ alias perle
alias perle='perl -Mstrict -Mwarnings -Mautodie=:all -E'
I first tried a cut-down version of your issue three different ways.
All gave the correct slice; only the third had no warning message.
$ perle 'use constant X => (1,3); my @y = "a".."z"; say for @y[X]'
Scalar value @y[X] better written as $y[X] at -e line 1.
$ perle 'use constant X => (1,3); my @y = "a".."z"; say for @y[+X]'
Scalar value @y[+X] better written as $y[+X] at -e line 1.
$ perle 'use constant X => (1,3); my @y = "a".."z"; say for @y[X()]'
I then looked at these sections of constant:
The first of those (see the WEEKDAYS example) suggested a fourth way to try;
this gave the correct slice and no error:
$ perle 'use constant X => 1,3; my @y = "a".."z"; say for @y[(X)]'
The second has:
"List constants are not inlined unless you are using Perl v5.20 or higher."
This perhaps suggests why [X] (and probably [+X]) had problems;
although I'm very much guessing here and don't really know what's going on under the hood.
Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
Want more info? How to link or
or How to display code and escape characters
are good places to start.