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Because the filepointer is in sync with the parsing phases of Perl
Not necessarily, no... Let's see
BEGIN { print "BEGIN\n"; } UNITCHECK { print "UNITCHECK\n"; } CHECK { print "CHECK\n"; } INIT { print "INIT\n"; } print "MAIN\n";
Let's strace it (Debian Jessie, Perl 5.22)
open("", O_RDONLY) = 3 ... read(3, "BEGIN {\n print \"BEGIN\\n\";\n}\nU"..., 8192) = 146 write(1, "BEGIN\n", 6) = 6 read(3, "", 8192) = 0 close(3) = 0 write(1, "UNITCHECK\n", 10) = 10 write(1, "CHECK\n", 6) = 6 write(1, "INIT\n", 5) = 5 write(1, "MAIN\n", 5) = 5
Note that the file is closed right after BEGIN (and before UNITCHECK). So no handle to it can exist. But, if we add
__DATA__ whatever
that it changes a bit...
open("", O_RDONLY) = 3 ... read(3, "BEGIN {\n print \"BEGIN\\n\";\n}\nU"..., 8192) = 165 write(1, "BEGIN\n", 6) = 6 fcntl(3, F_SETFD, FD_CLOEXEC) = 0 write(1, "UNITCHECK\n", 10) = 10 write(1, "CHECK\n", 6) = 6 write(1, "INIT\n", 5) = 5 write(1, "MAIN\n", 5) = 5 ... close(3) = 0 exit_group(0) = ?
Now the file isn't closed until exit. So without __DATA__ there is no handle to the file, and the only handle (that I can find :) is DATA.

Anyway, let us know if you'll find something in or somewhere else.

In reply to Re^3: Introsepcting the current Perl file via DATA, even w/o DATA? by Anonymous Monk
in thread Introspecting the current Perl file via DATA, even w/o DATA? by LanX

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