One other option, for those not wanting to modify their scripts at all: The PERL5LIB environment variable. If you do this:
perl -e "print join(qq|:|, @INC)"
you'll get your current perl @INC array in a path format. If you set your PERL5LIB env var to the output of that one-liner and also tack your own custom libs on the end of it, this will have the effect of putting a copy of your @INC in front of your custom libs, even though your original @INC remains untouched (and unused) at runtime. When I do this, my PERL5LIB ends up looking like this (breaks added for readability):
/usr/lib/perl5/5.6.1/i386-linux:/usr/lib/perl5/5.6.1:
/usr/lib/perl5/site_perl/5.6.1/i386-linux:
/usr/lib/perl5/site_perl/5.6.1:/usr/lib/perl5/site_perl:.:
/home/jtillman/customlibdir/
It ends up doubling your original @INC path in memory, but as a temporary measure, it's much easier to reverse, since you have no code to modify. Just a thought...
jpt