I want to be able to take arbitrary lines containing variables that are defined in the program, and interpolate them. 
#!/usr/bin/env perl
use 5.010;
use warnings;
use strict;

my $var1 = "abel";
my $var2 = "baker";
my $var3 = "charlie";

while (my $line = <DATA>) {
    chomp $line;
    say "Before interpolation: $line";
    say "After interpolation:  " . perform_interpolation($line);
    say '';
}

sub perform_interpolation {
    my $text = shift;
    # now what?
}

__DATA__
I'd like to see this one: $var1.
How about \$var3? You shouldn't interpolate \$var3 (but it would be ni
+ce if you'd remove the backslash)
Try a concatenation: $var1$var2

[download]
I've seen String::Interpolate mentioned in my searches, but unless I'm misunderstanding something, I'd have to know in advance what variables I'd be interpolating

What I'm trying to do is create a program template where a comment block right after the shebang line (possibly containing scalar variables like $program or other constants or environment variables) can be rendered to produce a usage statement.

The perform_interpolation() subroutine would be part of the template and wouldn't know specifically what variables the programmer might want to interpolate for the usage statement.

Can String::Interpolate do this? Or is there a simpler way?

In reply to Invoke the Perl string interpolation engine on a string contained in a scalar variable. by ibm1620

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.