Something New Every Day
Just now,
while attempting to do
print "$user's crontab is missing!\n"
I got the
error “Use of uninitialized value in concatenation (.) or string…”, and after a
bit of testing, I discovered that “$package'varname” is
apparently an alias of “$package::varname” (in my case,
Perl was trying—and failing—to print $user::s).
Did everyone else know this? This is literally the first time I have run across this in almost 20 years of Perl programming
(Of course a quick Google search turns this up in the opening paragraphs of the perlmod docs—I wonder if it’s time to read all of that stuff cover-to-cover?)
My real name is Jeremy Holland. I've been a programmer for 25 years, using primarily Perl since 2000.
I only know it because the books I read for Perl 5.6 mentioned the apostrophe as an archaic and now-outdated package separator and admonished me to use double-colon. So, I suspect it is not something everyone knows, but nowadays I expect it's something most people learn about through doing what you did.
I think you meant to write:
It's a little-known corner of Perl history. But it can be used for CPAN jokes.
Sometimes it seems like everybody knows, other times I’m surprised how many don’t.
Typo fixed. Thanks!
Note that in Perl 6, apostropes are valid parts of identifiers (with some restrictions
on their placement), so the issue that bit OP in Perl 6 complains about
undeclared variable `$user's` and uses Levenshtein distance to figure out that user might have meant the `$user` variable and suggests that.
There's something to be said for braces whenever a variable bumps up against anything that !~ m/\s/:
print "${user}'s crontab is missing!\n"
I partially agree, but clarity first and foremost, and I would argue that
print "$timestamp,$username,$operation,$result\n"
is more readable than
print "${timestamp},${username},${operation},${result}\n"
The JAPH in my .sig is based on this feature:
for(ref bless{},just'another'perl'hacker){s-:+-$"-g&&print$_.$/}Clever!