#! perl -slw
use strict;
$|++;                # Disable buffering on STDOUT for demo

my $re_multi = qr[    # Match 3 lines
    ^name\s*\n        # First starts with "name"  (and maybe some whit
+espace?
    ^-+\n            # Second consists entirely of '-'s
    (^.+)\n            # Third has the stuff we want so capture to $1
]mx;                # Allow match across line boundries.
                    # Ignore incidental white space

my $buffer = '';    # Init our buffer to null

# Grab a managable chunk of data.
# 16 is silly for demo only.
# My test show that 32/64 k seems about right on my system.
# The length() call ensures residual is retained

while (sysread( DATA, $buffer, 16, length $buffer)) {

    #     find all occurances in buffer.

    while($buffer =~ m[$re_multi]g ) {

        print $1;    # Do something with them

        # stop the buffer grwing bigger than necessary
        # by discarding everything upto the end of the last match

        $buffer = substr($buffer, pos($buffer) );
    }

    # This line defends against the buffer growing very large if two o
+ccurances
    # of the pattern are a very long way apart in the file.
    # It works (in the case) by discarding stuff that that cannot be p
+art
    # of what we are looking for (and could probably be improved upon)
+.
    # This must be tailored on a case-by-case basis.

    $buffer = substr( $buffer, pos($buffer) -1 ) if $buffer =~ m[\n(?!
+name)]gc;
}

__DATA__
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and 
+irrelevent crap
name
----------------------------------------
1 23 4.5 678e9
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and 
+irrelevent crap
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and 
+irrelevent crap
name
----------------------------------------
1 23 4.5 678e9
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and 
+irrelevent crap
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and 
+irrelevent crap
name
----------------------------------------
1 23 4.5 678e9
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and 
+irrelevent crap
[download]