Horizontally, Abigail-II's code looks like this:
perl -lpe '}{*_=*.}{' file
Which is really quite beautiful.
Anyway, it (ab)uses the way that the -p command line option works. Consider the following output from deparse:
$ perl -MO=Deparse -lpe '' file
LINE: while (defined($_ = <ARGV>)) {
chomp $_;
}
continue {
print $_;
}
So for a simple bare -p you get all of that extra and useful code.
Now if we deparse Abigail-II's code:
$ perl -MO=Deparse -lpe '}{*_=*.}{' file
LINE: while (defined($_ = <ARGV>)) {
chomp $_;
}
{
*_ = *.;
}
{
();
}
continue {
die "-p destination: $!\n" unless print $_;
}
The addition of the extra braces has created a while loop that loops through the file(s), a block with an assignment and a block with an empty statement and a continue. In effect it has disassociated the continue from the while.
The typeglob assignment *_ = *. has the effect, among other things, of setting $_ = $.. Since the while has already looped through the file(s) $. is now the number of lines in the file(s).
The last action of the program will be to enter the continue and print $_ so that the number of lines is output. The -l command line option helpfully appends a newline.
Update: Abigail-II's own explanation is here
John.
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