I'm using a library that acts on an %ENV variable being either set or not set. So, when I call it, I use 

    local $ENV{BLAH} = 42;
    libcall();

    sub libcall {
        if( exists $ENV{BLAH} ) {
            print "env set to $ENV{BLAH}\n";
        } else {
            print "env not set\n";
        }
    }

[download]

and all is well, because the code within libcall() now sees $ENV{BLAH}'s value, while other parts of the system (outside the scope of the snippet above) aren't affected by the setting.

But now I want to add a condition in my code, to perform the setting only when another condition is met, but I can't use 

    if( condition() ) {
        local $ENV{BLAH} = 42;
    }
    libcall();

[download]

because the 'local' directive ends with the scope of the if-body and libcall() won't see it. I can't set the variable to undef because the library checks if the value exists(). I could obviously do 

    if( condition() ) {
        local $ENV{BLAH} = 42;
        libcall();
    } else {
        libcall();
    }

[download]

but that's lame because of the code duplication.

Is there a better way to 'local'ize a variable conditionally?

In reply to How to localize conditionally? by saintmike

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.