Re^5: perldoc -lf anomaly (%

> So why isn't it documented?

Because contrary to $_ and @_ it has no function

> I could swear I saw it somewhere once upon a time, or maybe not...

People are exploiting the side effect that it's a global and doesn't need to be declared.

> What is it???

The typeglob / symbol _ is global to allow the scalar and array slots $_ and @_ to hold magic.

The hash slot is undefined but still global and can be (ab)used for syntactic sugar.

# No my/our %_ lives in  main::
%_ = (a => 1, b => 2);   # global variable in package main
[download]

perldoc -v and perlvar should probably be expanded to show a generic explanation for such "reserved" special variables

Cheers Rolf
_{(addicted to the Perl Programming Language :)

see Wikisyntax for the Monastery}

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Re^6: perldoc -lf anomaly (%_) by LanX (Saint) on May 08, 2026 at 12:19 UTC
Follow up: I just noticed that while `@ENV` is reserved special, `@a` is not. Compare `%ENV` and `$a` ... Has this always been the case? I kind of remember @a being "weird" too. `$ perl -e'use strict;@1=(666)' $ perl -e'use strict;@STDOUT=(666)' $ perl -e'use strict;@ENV=(666)' #but $ perl -e'use strict;@a=(42)' Global symbol "@a" req +uires explicit package name (did you forget to declare "my @a"?) at - +e line 1. $ perl -e'print $]' 5.040003$` [download] Cheers Rolf _{(addicted to the Perl Programming Language :) see Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^7: perldoc -lf anomaly (%_) by choroba (Cardinal) on May 08, 2026 at 12:46 UTC
I think that's because `$a` and `$b` are package variables, not globals. Same with `@F` under `-a`. `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l] [select]
Re^8: perldoc -lf anomaly (%_) by LanX (Saint) on May 08, 2026 at 13:02 UTC
Hmm yes, $a and $b live - if needed - in the current package and not `main::` `$ perl -E'package tst; sort{$a le $b} 1..100; say exists $tst::{a}; us +e strict; say $a;' 1` [download] Cheers Rolf _{(addicted to the Perl Programming Language :) see Wikisyntax for the Monastery}	[reply] [d/l] [select]