++ Thanks for your response.

I only started using PERL5OPT a few weeks ago because I was sick of having to add those pragmata whenever I wanted a quick one-liner.

The "perlrun: PERL5OPT" documentation starts:

"Command-line options (switches). Switches in this variable are treated as if they were on every Perl command line."

I took this to mean that (with my current PERL5OPT settings)

perl -E '...'
[download]

would be expanded to

perl -Mstrict -Mwarnings -Mautodie -E '...'
[download]

I ran quite a few tests and, when satisfied everything worked OK, modified my .bash_profile so that it would always be available.

It never occurred to me that this would affect scripts; however, following your comments, I've run additional script tests and it does appear that my shebang line

#!/usr/bin/env perl
[download]

is being altered to

#!/usr/bin/env perl -Mstrict -Mwarnings -Mautodie
[download]

As I always add strict and warnings to every script, and often add autodie, this is not a problem for me. So, while I thank you for alerting me to this, I will continue to use PERL5OPT as I'm currently doing unless I come across a good reason for not doing so.

"It makes your scripts non-portable."

Perhaps you could expand on this. I'm failing to see any portability issues.