In your library definition, you used the fat comma; however, that stringifies everything on the left. So here you need a good, old-fashioned comma. Also, MooseX::Types doesn't automatically use strict or use warnings. So here's my take on it: 
package MyTypes;

use 5.010;
use strict;
use warnings;
use MooseX::Types -declare => [qw( ExistingFile DataFromFile )];
use MooseX::Types::Moose qw( ArrayRef Str );
use Tie::File;

subtype ExistingFile, as Str,
  where { -e },
  message { "file '$_' does not exist" };

subtype DataFromFile, as ArrayRef,
  where { ref $_ eq "ARRAY" },
  message { "argument is not an ArrayRef" };

coerce DataFromFile,
  from ExistingFile,
  via { tie my @array, "Tie::File", $_; return \@array };

1;

[download]

In reply to Re: MooseX-Types warnings by Khen1950fx
in thread MooseX-Types warnings by j1n3l0

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.