/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;
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is almost the same as saying

    BEGIN { unshift(@INC, LIST) }
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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