Hashes are unordered by default in Perl 5. You can use tie and Tie::IxHash to override this behavior. Be warned though, there is a performance hit and other considerations (like the fact that the order will not be preserved in copies). #!/usr/bin/perl use strict; use warnings; use Tie::IxHash; tie my %hash, “Tie::IxHash” or die “could … Read more
Using new Some::Class is called “indirect” method invocation, and it’s bad because it introduces some ambiguity into the syntax. One reason it can fail is if you have an array or hash of objects. You might expect dosomethingwith $hashref->{obj} to be equal to $hashref->{obj}->dosomethingwith(); but it actually parses as: $hashref->dosomethingwith->{obj} which probably isn’t what you … Read more
Have a look at perldiag: Global symbol “%s” requires explicit package name (F) You’ve said “use strict” or “use strict vars”, which indicates that all variables must either be lexically scoped (using “my” or “state”), declared beforehand using “our”, or explicitly qualified to say which package the global variable is in (using “::”).
The => operator in perl is basically the same as comma. The only difference is that if there’s an unquoted word on the left, it’s treated like a quoted word. So you could have written Martin => 28 which would be the same as ‘Martin’, 28. You can make a hash from any even-length list, … Read more
Use require to load modules at runtime. It often a good idea to wrap this in a block (not string) eval in case the module can’t be loaded. eval { require My::Module; My::Module->import(); 1; } or do { my $error = $@; # Module load failed. You could recover, try loading # an alternate module, … Read more
Quick Answer (TL;DR) %hash1 = (%hash1, %hash2) ## or else … @hash1{keys %hash2} = values %hash2; ## or with references … $hash_ref1 = { %$hash_ref1, %$hash_ref2 }; Overview Context: Perl 5.x Problem: The user wishes to merge two hashes1 into a single variable Solution use the syntax above for simple variables use Hash::Merge for complex … Read more
You can daemonize any executable in Unix by using nohup and the & operator: nohup yourScript.sh script args& The nohup command allows you to shut down your shell session without it killing your script, while the & places your script in the background so you get a shell prompt to continue your session. The only … Read more
This was exactly the challenge that David Golden faced when he wrote Capture::Tiny. I think it will help you do exactly what you need. Basic example: #!/usr/bin/env perl use strict; use warnings; use Capture::Tiny ‘capture’; my ($stdout, $stderr, $return) = capture { system( ‘echo Hello’ ); }; print “STDOUT: $stdout\n”; print “STDERR: $stderr\n”; print “Return: … Read more
I suggest you use List::Permutor: use List::Permutor; my $permutor = List::Permutor->new( 0, 1, 2); while ( my @permutation = $permutor->next() ) { print “@permutation\n”; }
Clone is much faster than Storable::dclone, but the latter supports more data types. Clone::Fast and Clone::More are pretty much equivalent if memory serves me right, but less feature complete than even Clone, and Scalar::Util::Clone supports even less but IIRC is the fastest of them all for some structures. With respect to readability these should all … Read more