but I am going to take a deep breath and code up the with-g and without-g cases separately
What is the obsession of people to try and solve a complex problem like this in a single line of code, just because it can be done in one line of code in a perl script? I don't mean you specifically, but in general, like apparently most people who replied to this thread.

Splitting this up in two parts makes sense, using /g is not a modifier of the pattern (as it is in several other languages), but of the substitution. Something like this looks acceptable to me as the (obvious) redundancy is actually quite limited: 

    if($flages =~ s/g//) {
        s/(?:$flags)$pattern/replacement($replacement)/ge;
    }
    else {
        s/(?:$flags)$pattern/replacement($replacement)/e;
    }

[download]
where you still have to provide the sub replacement.

Other flags cannot really coded this way, but there's no need to provide for /o or /r at all, and allowing people to use /e flag in a config file, simply looks dangerous to me. If people would really want to use /e, it likely would be for just a handful of specific cases, and you can instead code a simpler solution for those cases (for the user, not necessarily for you) explicitly in your script, than having them write convoluted perl code.

That real danger of allowing ordinary users to run arbitrary code, is also why I really don't like use of eval. It also enforces taking special care to be taken when writing the sub replacement. You can mitigate the danger by using a module like String::Interpolate, to embed captured values while disallowing access to the rest of the intestines of the script. .

In reply to Re^3: Regexp substitution using variables by bart
in thread Regexp substitution using variables by MikeTaylor

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.