I've been working on a "quick and dirty" script that should run from .bashrc. It seemed a lot slower than an equivalent bash script (which runs several executables...), so I decided to time it. It turned out the code itself didn't really make a difference -- it was the imports that were sluggish.

In particular, just importing (without using at all) autodie, Pod::Usage and Getopt::Long will slow down a do-nothing program. Here are the results from hyperfine (-adie means enable autodie, -podu = Pod::Usage, and -go = Getopt::Long; actual programs at the end)

Benchmark 1: /tmp/x-go-adie-podu.pl
  Time (mean ± s):   107.1 ms ±   0.5 ms [User: 94.5 ms, Sys: 12.5 ms]
  Range (min … max): 106.2 ms … 108.1 ms 27 runs

Benchmark 2: /tmp/x-go-adie.pl
  Time (mean ± s):   50.2 ms ±   0.2 ms [User: 44.5 ms, Sys: 5.7 ms]
  Range (min … max): 49.7 ms …  50.6 ms 58 runs

Benchmark 3: /tmp/x-go.pl
  Time (mean ± s):   25.7 ms ±   0.1 ms [User: 21.6 ms, Sys: 4.1 ms]
  Range (min … max): 25.5 ms …  25.9 ms 112 runs

Benchmark 4: /tmp/x.pl
  Time (mean ± s):    7.8 ms ±   0.1 ms [User: 5.3 ms, Sys: 2.5 ms]
  Range (min … max):  7.6 ms …   8.1 ms 324 runs
[download]

So, we jump from 8ms to 25ms to 50ms to 107ms just by importing (in order) Getopt::Long, autodie, and Pod::Usage. Once it reaches tenths-of-a-second territory I get itchy, because it's starting to become visible to humans.

Anyway

• why are these so slow to import?
• can they be easily replaced? I could ditch autodie; I could use perldoc to pre-generate the usage message; but I'd rather not hand-code an arg parsing loop.

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Actual files:

### /tmp/x-go-adie-podu.pl
#!/usr/bin/env perl
use strict; use warnings;
use Getopt::Long qw( :config );
use Pod::Usage;
use autodie;

### /tmp/x-go-adie.pl
#!/usr/bin/env perl
use strict; use warnings;
use Getopt::Long qw( :config );
use autodie;

### /tmp/x-go.pl
#!/usr/bin/env perl
use strict; use warnings;
use Getopt::Long qw( :config );

### /tmp/x.pl
#!/usr/bin/env perl
use strict; use warnings;
[download]

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