FAQ 6.4: I put a regular expression into $/ but it didn't work. What's wrong?

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6.4: I put a regular expression into $/ but it didn't work. What's wrong?

Up to Perl 5.8.0, $/ has to be a string. This may change in 5.10, but
don't get your hopes up. Until then, you can use these examples if you
really need to do this.

Use the four argument form of sysread to continually add to a buffer.
After you add to the buffer, you check if you have a complete line
(using your regular expression).

local $_ = "";
while( sysread FH, $_, 8192, length ) {
while( s/^((?s).*?)your_pattern/ ) {
my $record = $1;
# do stuff here.
}
}

You can do the same thing with foreach and a match using the
c flag and the \G anchor, if you do not mind your entire file
being in memory at the end.

local $_ = "";
while( sysread FH, $_, 8192, length ) {
foreach my $record ( m/\G((?s).*?)your_pattern/gc ) {
# do stuff here.
}
substr( $_, 0, pos ) = "" if pos;
}



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