Alright, one remark up front: read up on the difference between eval {block} and eval $string. It's crucial.

But also consider this: eval $string is for interpreting strings as code, not for variable substitution. Let's say you've got a string

my $string = 'some $stuff I want to $interpolate';
You can now eval $string to interpolate $stuff and $interpolate, but... You need to add quotes:

my $value = eval "'$string'";
update there's a bug here. read ikegami's reply.

The problem with this, is that you can't know if there are any quotes in $string, so you need to escape the quotes in $string before eval()ing. Also, it will interpolate anything that looks like a variable. Even if the variable in question shouldn't be interpolated at all.

In general, if you want to give your users the maximum amount of control, use eval. In any other case, you're better off using a templating language. You might even use something like Text::Template, which is fast and works more or less like perl. If you want to use something simple that's more strict in its input, use something like GrandFather's post.


In reply to Re^3: Form letters: eval a string to substutite perl variables by Joost
in thread Form letters: eval a string to substutite perl variables by brycen

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.