Use experimental Perl feature: #!/usr/bin/perl use Modern::Perl '2015'; use feature qw(signatures); no warnings qw(experimental::signatures); sub

Use experimental Perl feature: #!/usr/bin/perl use Modern::Perl '2015'; use feature qw(signatures); no warnings qw(experimental::signatures); sub foo($bar, $baz) { $bar+$baz } say foo(40, 2); See `man feature` for details. Or use CPAN modules: https://metacpan.org/pod/signatures https://metacpan.org/pod/signatures , https://metacpan.org/pod/Function::Parameters https://metacpan.org/pod/Function::Parameters