Perl 5.8.0, w/PerlIO, Linux 2.4:

$ ./diamond
Benchmark: timing 100 iterations of readbig, whilelp...
   readbig: 10 wallclock secs ( 8.07 usr +  0.29 sys =  8.36 CPU) @ 11
+.96/s (n=100)
   whilelp:  5 wallclock secs ( 4.79 usr +  0.29 sys =  5.08 CPU) @ 19
+.69/s (n=100)
$
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PerlIO certainly appears to be a big improvement. Several runs show a scatter of +/- 0.10/sec in the results. My test file was 8000 lines of 65 characters.

After Compline,
Zaxo