-E behavior with stdin script

almr has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks

it's never been quite clear to me how to get full -E behavior with a stdin script. Let's call perl from a shell script (this the reason for not wanting -E, and some other choices):

perl -Mv5.12 -wn -- - /etc/passwd <<'EOF'
next unless / ([^:]*) : [^:]* : ([0-9]+) /x;
my ($w, $n) = (uc $1, 5000 + $2);
say qq{log=$w id=$n}
EOF
[download]

As I understand it, -E turns on optionals (e.g. say, <<>>), but also some behaviors (e.g. use strict, Unicode handling). Now the unpalatable choices become

specify a "minimal minimum" version (e.g. -Mv.5.12) to get say and strict; but that probably disables post-5.12 changes
specify a "maximal minimum" version (e.g. -Mv5.28), but that fails for older Perls
use -E with an inline single- / double-quoted shell string, with all the niceties of shell quoting / escaping
use -E with a wastefull -E "$(cat <<"EOF" ... )"

Are there any other options to get -E behavior without -E?

Comment on -E behavior with stdin script Select or Download Code

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Re: -E behavior with stdin script (updated x2!) by haukex (Bishop) on Sep 05, 2021 at 07:42 UTC
Note `-E` doesn't turn on strict, ~~AFAICT its equivalent is `-Mfeature=:all`~~. Update: Sorry, that's not quite right - `:all` also enables experimental features and features that were removed from feature bundles of later versions, like `array_base`. ~~I showed a slightly hackish workaround here.~~ Update 2: Here's an improved version that gives exactly the same result as the `-E` switch: `use Config; use feature ":$Config{PERL_REVISION}.$Config{PERL_VERSION}";` [download]	[reply] [d/l] [select]
Re^2: -E behavior with stdin script by almr (Acolyte) on Sep 05, 2021 at 09:28 UTC
Ah. I was getting confused. So the least-verbose choices become, I think, `[-Mstrict] -Mfeature=:all -- - <<EOF` to run a stdin script `[-Mstrict] -E script` to run a stringified script `-Mv5.28 {-e script \| -- -}` (as of now) to require a recent perl with all security & unicode fixes, turn on `strict`, and run either a stdin or a stringified script.	[reply] [d/l] [select]
Re^3: -E behavior with stdin script by NERDVANA (Pilgrim) on Sep 05, 2021 at 13:03 UTC
The least verbose option would be -MMyDefaults, where you write a module named MyDefaults that sets all the bits as you prefer and then you install that on each system you use :-)	[reply]
Re^3: -E behavior with stdin script by haukex (Bishop) on Sep 05, 2021 at 13:53 UTC
`-Mfeature=:all` Sorry, I made a mistake, that's actually not exactly equivalent to `-E`, please see the updates in my node above.	[reply] [d/l] [select]
Re: -E behavior with stdin script by salva (Canon) on Sep 05, 2021 at 11:51 UTC
AFAIK, there is no way to pick the features enabled by `-E` automatically other than by using it. But you can require just what you need inside the code chunk: `perl -wn -- - /etc/passwd <<'EOF' use feature 'say'; next unless / ([^:]) : [^:] : ([0-9]+) /x; my ($w, $n) = (uc $1, 5000 + $2); say qq{log=$w id=$n} EOF` [download] That's the most future-proof solution.	[reply] [d/l] [select]
Re^2: -E behavior with stdin script (updated) by haukex (Bishop) on Sep 05, 2021 at 13:50 UTC
AFAIK, there is no way to pick the features enabled by -E automatically other than by using it. Well, `-E` is equivalent to a `use feature ':5.XX';`, so one slightly hackish way to get the same effect is `use feature ":5.".(0+substr($],2,3));`. Update: Crossposting the following better solution from my other node for completeness: `use Config; use feature ":$Config{PERL_REVISION}.$Config{PERL_VERSION}";` [download]	[reply] [d/l] [select]
Re: -E behavior with stdin script by BillKSmith (Monsignor) on Sep 05, 2021 at 12:58 UTC
The module Modern::Perl addresses a similar issue. I do not know if you could use it, but its documentation may be helpful. Bill	[reply]
Re: -E behavior with stdin script by ikegami (Patriarch) on Sep 05, 2021 at 19:15 UTC
You really shouldn't be using `-E` outside of throwaway single-use code. The problem with `-E` is that it's not forward-compatible. It defies the whole feature mechanism by enabling the highest possible feature set, breaking programs the feature mechanism is supposed to protect. It's great for throwaway single-use code, but not for production code. You should use the appropriate feature set and/or version for your program. `-M5.010` / `use 5.010;` would suffice for the posted example (although all higher versions that exist at this time would also work). Seeking work! You can reach me at ikegami@adaelis.com	[reply] [d/l] [select]
Re: -E behavior with stdin script by Anonymous Monk on Sep 05, 2021 at 14:31 UTC
Sitecustomize Re: batch 'use' possible? (perl5.pm Toolset.pm, Syntax::Collector , Toolkit.pm, rig.pm, sitecustomize.pl, PERL5OPT )( load multiple commonly-used favorite modules in a single import expression )...	[reply]


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