Not sure what you're expecting to happen when you say it didn't change.  Are you expecting to manipulate @INC permanently?  That's not how it works.  use lib ... changes @INC only for the lifetime of the script.  Also, use lib doesn't take a space-separated string of directories, but a list of directories, if you need more than one.

Consider this:

#!/usr/bin/perl -wl
use strict;

BEGIN { print for @INC; print "-----" }
use lib "/usr/share/perl5/vendor_perl/AnyEvent/Iml", "/foo/bar";
BEGIN { print for @INC; print "-----" }

# use here whatever module lives in one of the added paths...
[download]

$ ./955116.pl
/etc/perl
/usr/local/lib/perl/5.12.4
/usr/local/share/perl/5.12.4
/usr/lib/perl5
/usr/share/perl5
/usr/lib/perl/5.12
/usr/share/perl/5.12
/usr/local/lib/site_perl
.
-----
/usr/share/perl5/vendor_perl/AnyEvent/Iml
/foo/bar
/etc/perl
/usr/local/lib/perl/5.12.4
/usr/local/share/perl/5.12.4
/usr/lib/perl5
/usr/share/perl5
/usr/lib/perl/5.12
/usr/share/perl/5.12
/usr/local/lib/site_perl
.
-----
[download]

As you can see in the second printout of @INC (after the use lib), the two directories have been added.

___

P.S.:  please use <p>...</p> (text paragraph) and <c>...</c> (code) tags to format your posts.

For example, typing

<p> inserting into the script: </p>
<c>
use lib "/usr/share/perl5/vendor_perl/AnyEvent/Iml";
</c>
<p> also does not change the entry. </p>
[download]

will render as

inserting into the script:

use lib "/usr/share/perl5/vendor_perl/AnyEvent/Iml";
[download]

also does not change the entry.

I added your code at the start of the script and the module was found! Now I have a new problem. The script (not mine) generates this error:

Bareword "Tk::MainLoop" not allowed while "strict subs" in use at /usr
+/share/perl5/vendor_perl/AnyEvent/Impl/Tk.pm line 134.
Compilation failed in require at ./guiguts.pl line 49.
BEGIN failed--compilation aborted at ./guiguts.pl line 49.
[download]

Line 49 is Tk.pm which is the module in the directory needed in @INC