Category: miscellany

Perl v5.34 allows you to specify octal literals with the 0o prefix, as in 0o123_456. This is consistent with the existing constructs to specify hexadecimal literal 0xddddd and binary literal 0bddddd. The builtin oct() function accepts any of these forms.

Previously, you specified octal with just a leading zero:

chmod 0644, $file;
mkdir 0755, $file;

Now you can do that an extra character that specifies the base:

chmod 0o644, $file;
mkdir 0o755, $file;

This makes it consistent with 0b for binary and 0x for hexadecimal. See “Scalar value constructors” in perldata.

And, remember that v5.14 added the \o{NNN} notation to specify characters by their octal number. We’re still waiting for octal floating point values (we got the hex version in v5.22), but don’t hold your breath.

Perhaps we’ll get 0d sometime so that all the bases.

Perl v5.20 introduced key-value slices that worked on hashes and arrays. You could extract values by their keys or indices as well as assigning to those.

The key-value slice delete is way to extract the keys and values you want and delete them at the same time. You can destructively
Continue reading “Perl v5.28 can delete key-value slices”

In-place editing is getting much safer in v5.28. Before that, in rare circumstances it could lose data. You may have never noticed the problem and even with all the times I’ve explained it in a Perl class I haven’t really thought about it. This was first reported as early as December 2002 and after we get v5.28 it won’t be a problem anymore. Continue reading “In-place editing gets safer in v5.28”

Starting in v5.26, a hash in scalar context evaluates to the number of keys in the hash. You might have thought that it always did that just like an array (not a list!) in scalar context evaluates to the number of items. But nope—it evaluated to a seemingly useless number called the “hash statistics”. Now it’s fixed to do what most people thought it already did. For what it’s worth, keys (or values) in scalar context already provided the count.

Continue reading “keys in scalar context now returns the number of keys”

[This feature is no longer experimental, starting in v5.28. Declaring use 5.28 automatically enables them.]

Most Perl operators force their context on the values. For example, the numeric addition operator, +, forces its values to be numbers. To “add” strings, you use a separate operator, the string concatenation operator, . (which looks odd at the end of a sentence).

The bitwise operators, however, look at the value to determine their context. With a lefthand value that has a numeric component, the bitwise operators do numeric things. With a lefthand value that’s a string, the bit operators become string operators. That’s certainly one of Perl’s warts, which I’ll fix at the end of this article with a new feature from v5.22. Continue reading “Make bitwise operators always use numeric context”

Not sure which loop you want to break out of? Perl v5.18 makes that easy with computed labels. The value you give next, last, and redo no longer has to be a literal. You could already do this with goto, but now you can give the loop controllers an expression. Continue reading “Use a computed label with loop controllers”