dear monks: I want to work with a template that has access to all my perl variables that are of the form '\$\w+', but nothing else. I understand that there are templating systems that do this more professionally, but I want it quick-and-dirty. one-liners are appealing!

now, the below code fragment works, except when a variable is not defined. so how do I handle undefined variables? 

use warnings FATAL => qw{ uninitialized };

my $abc = "ABC";
my $def = "DEF";
## no $ghi is defined.

my $funnystring= '
   hello $abc and $def and $ghi';
$funnystring =~ s/(\$\w+)/"defined($1) ? $1 : 'unknown $1'"/gee;
print $funnystring;

[download]
(I could turn the warning off, but then I lose the flexibility of writing something that describes the undefined variable.) /iaw

In reply to super-simple regex-based template eval --- handling undefined substitutions by iaw4

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.