Pre-allocating the string sounds like a good idea, but in order to make it work, you then need to ensure that you overwrite the pre-allocated contents, not add to or replace them.
Two ways you might do this are substr and vec used as lvaues, but the reality (on my system:) is that using either is way slower than allowing perl to manage the process itself.
C:\test>241328
Name "main::substr" used only once: possible typo at C:\test\241328.pl
+ line 6.
Name "main::bytewise" used only once: possible typo at C:\test\241328.
+pl line 5.
Name "main::vec" used only once: possible typo at C:\test\241328.pl li
+ne 7.
Benchmark:
running
bytewise, substr, vec
, each for at least 5 CPU seconds
...
bytewise: 5 wallclock secs ( 5.17 usr + 0.01 sys = 5.18 CPU) @ 1
+.55/s (n=8)
Use of uninitialized value in substr at (eval 6) line 1.
substr: 6 wallclock secs ( 6.05 usr + 0.00 sys = 6.05 CPU) @ 0
+.83/s (n=5)
vec: 6 wallclock secs ( 5.22 usr + 0.00 sys = 5.22 CPU) @ 0
+.96/s (n=5)
s/iter substr vec bytewise
substr 1.21 -- -14% -47%
vec 1.04 16% -- -38%
bytewise 0.647 87% 61% --
C:\test>
I suspect that the best answer is to try and avoid producing your data 1 byte at a time. If you identified that process, there might be alternative ways of acheiving it more efficiently.
Examine what is said, not who speaks.
1) When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
2) The only way of discovering the limits of the possible is to venture a little way past them into the impossible
3) Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke.
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