Effective Perl Programming – write better, more idiomatic Perl
This is a chapter in Perl New Features, a book from Perl School that you can buy on LeanPub or Amazon. Your support helps me to produce more content.
Perl’s general regex quantifier, {n,m} takes a minimum and maximum number of matches. If you leave out the maximum number, like {n,}, you have to match the preceding thing at least n times but as many times as it can match: the maximum is unbounded.
These items are in Perl New Features, a book from Perl School that you can buy on LeanPub or Amazon. Your support helps me to produce more content.
use v5.38class feature${^LAST_SUCCESSFUL_PATTERN} variablePerl 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.
This is a chapter in Perl New Features, a book from Perl School that you can buy on LeanPub or Amazon. Your support helps me to produce more content.
0o prefixtry-catch syntax{,m} regex quantifier\x{...} and {n,m}And, I’ll update the Perl New Features for v5.34 too.
Not all characters with a numerical value are “digits”, in the Perl sense. You saw in Match Unicode characters by property value, in which you selected characters by a Unicode property value. That showed up again in Perl v5.18 adds character class set operations. Perl v5.30 adds a slightly easier way to get at multiple numerical values at the same time. Now you can match Unicode property values with wildcards (Unicode TR 18), which are sorta like Perl patterns. Don’t get too excited, though, because these can be expensive.
Continue reading “Match Unicode property values with a wildcard”
Perl has some of the best Unicode support out there, and it keeps getting better. Perl v5.32 supports Unicode 13, and you can now apply patterns to character names. You probably don’t want to do that though.
First, the Unicode Character Database catalogs each character, giving it a code number, a name, and many other properties.
Continue reading “Match Unicode character names with a pattern”
Perl v5.32 adds a way to turn off a Perl feature that you shouldn’t use anyway. You can still use this feature, but now there’s a way to take it away from you.
Checking that a value is between two others involves two comparisons, and so far in Perl that’s meant that you’ve had to type one of the values more than once. That gets simpler in v5.32 with chained comparisons. This would make Perl one of the few languages that support the feature. So far its implemented in v5.31.10 and until v5.32 is actually released, it isn’t a real feature.
Continue reading “Chain comparisons to avoid excessive typing”
In Ignore part of a substitution’s match, I showed you the match resetting \K—it’s basically a variable-width positive lookbehind assertion. It’s a special feature to work around Perl’s lack of variable-width lookbehinds. However, v5.30 adds an experimental feature to allow a limited version of a variable-width lookbehind.
Continue reading “Use a variable-width lookbehind if it won’t match more than 255 characters”
Perl v5.32 is out and it has some interesting new features. The previous major releases focussed more on finally removing deprecations and shoring up odd cases, and you still find a few of those in this release. Full details, as always, are in the perldelta.
Sawyer X just announced Perl 7 as a major version jump that relabels what is now v5.32. If you’re code is ready for v5.32, you should be mostly ready for Perl 7.
isa infix operator (“class instance”)streamzip program comes with IO::Compress::Base, so it comes with perl"0" .. "-1" is fixed