/usr/bin/env perl

use strict;
use warnings;

BEGIN {
    unshift @INC, '~/perl5/lib/perl5';
}

use Excel::Writer::XSLX;
[download]

/usr/bin/env perl

use strict;
use warnings;
use Array::Contains;

BEGIN {
    if(contains('--debug', \@ARGV)) {
        print("Development INC activated\n\n");
        unshift @INC, '~/perl5/lib/perl5';
    }
}

use Excel::Writer::XSLX;
[download]

Did you try your examples? I don't think so.

Both are missing a shebang (#!) in line 1 and would cause a syntax error. Plus, as shown in Load module from local dir, neither manipulating @INC nor use lib expand the tilde. unshift never should, and use lib doesn't, at least not in my Perl:

/home/alex>cd /tmp/

/tmp>echo 'package Foo;1;' > ~/Foo.pm

/tmp>perl -E 'use Foo; say "ok"'
Can't locate Foo.pm in @INC (you may need to install the Foo module) (
+@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib
+64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /u
+sr/share/perl5 .) at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

/tmp>perl -E 'use lib "~"; use Foo; say "ok"'
Can't locate Foo.pm in @INC (you may need to install the Foo module) (
+@INC contains: ~ /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/l
+ib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 
+/usr/share/perl5 .) at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

/tmp>perl -E 'use lib "~/."; use Foo; say "ok"'
Can't locate Foo.pm in @INC (you may need to install the Foo module) (
+@INC contains: ~/. /usr/local/lib64/perl5 /usr/local/share/perl5 /usr
+/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl
+5 /usr/share/perl5 .) at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

/tmp>perl -E 'use lib $ENV{"HOME"}; use Foo; say "ok"'
ok

/tmp>perl -v

This is perl 5, version 22, subversion 2 (v5.22.2) built for x86_64-li
+nux-thread-multi

Copyright 1987-2015, Larry Wall

Perl may be copied only under the terms of either the Artistic License
+ or the
GNU General Public License, which may be found in the Perl 5 source ki
+t.

Complete documentation for Perl, including FAQ lists, should be found 
+on
this system using "man perl" or "perldoc perl".  If you have access to
+ the
Internet, point your browser at http://www.perl.org/, the Perl Home Pa
+ge.


/tmp>
[download]

And by the way:

Saying

    use lib LIST;
[download]

is almost the same as saying

    BEGIN { unshift(@INC, LIST) }
[download]

Except that newer versions of lib do some additional fancy stuff with architecture-specific directories:

For each directory in LIST (called $dir here) the lib module also checks to see if a directory called $dir/$archname/auto exists. If so the $dir/$archname directory is assumed to be a corresponding architecture specific directory and is added to @INC in front of $dir. lib.pm also checks if directories called $dir/$version and $dir/$version/$archname exist and adds these directories to @INC.

Also, if can be used to conditionally load other modules, including lib:

/tmp>perl -E 'use if -f(qq[$ENV{"HOME"}/Foo.pm]), lib => $ENV{"HOME"};
+ use Foo; say "ok"'
ok

/tmp>
[download]

Alexander

Damn! I know i shouldn't just copy&paste from my source repo without testing. Sorry!

"For me, programming in Perl is like my cooking. The result may not always taste nice, but it's quick, painless and it get's food on the table."