Error: BEGIN failed--compilation aborted

An often important general rule is that the first error message is usually the one that you want to pay attention to. The error message you quoted above is not the first error message you got. It is a follow-on error message that notes a consequence of the previous error and one that is particularly unenlightening here.

Please look at the first error message and it'd probably be good to reply to your node with the exact text of that first error message so the rest of us don't have to guess at what error you got (though, my guess is that you didn't declare the $override variable while you were smart enough to use strict, but that is just a guess -- further, I guess that you should just drop the [$override]s from your code).

You need to wrap your code in <code> and </code> tags. The characters [ and ] are special to perl monks and can't be put as literal text in your post. You should also use <p> and </p> tags around paragraphs.

At a guess you have cut and pasted this code from the documentation

Env::C::setenv($key, $value, [$override]);
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If you fix your post with code tags and an explanation of what your are trying to achieve you will get a better response. Please read How do I post a question effectively?.

Do you have Env::C installed? It's not a core module. If not, see How do I install a module from CPAN? in perlfaq8.

Thanks for fixing the format of your post++. As tye said it looks like Env::C is not installed but we'd need to see the full error message to be sure.

Are you sure that you need to use this module? As the documentation says

Sometimes Perl invokes modules with underlaying C APIs which rely on certain environment variables to be set, if these variables are set in Perl and the glue code doesn't worry to set them on the C level, these variables might not be seen by the C level. This module shows what really the C level sees.

Some examples

$ENV{IM_ROOT} =  $TC_ROOT;   # set IM_ROOT
$ENV{IM_DATA} |= $TC_DATA;   # set IM_DATA if not already set
system qw(program -switch argument);  # program sees new values of IM_
+ROOT and IM_DATA

{   # this value of IM_DATA is only seen while this block is executing
    local $ENV{IM_DATA} = $TC_DATA; 
    system qw(program -switch argument);
}
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