In my login script, I have

export PERL5LIB=~/lib/perl5
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To install a module, Pure Perl or otherwise, I do

perl Makefile.PL PREFIX=~ LIB=~/lib/perl5
make
make test
make install
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I actually use the cpan tool, which allows you to specify command line parameters for Makefile.PL. Do so (once) using:

o conf makepl_arg PREFIX=~ LIB=~/lib/perl5
o conf commit
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Caveat: PERL5LIB isn't honoured when taint checking is enabled. Add the following to such scripts to make them work:

use lib '/home/ikegami/lib/perl5';
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