The problem was coming back to Perl after spending a lot of time writing PHP code, where variables inside functions are locally scoped by default.

And where the only efficient loop over numbers is a C-style loop. Your example can do without variables completely:

sub foo {
    for (1..3) {
        print;
    }
    print "\n";
}

for (0..9) {
    foo;
}
[download]

Note that I also have put the sub at the top. If you put your sub at the bottom, _ALL_ lexicals that aren't in a block are shared by subs.

With for modifiers instead of for control structures, you can shorten your code even more:

sub foo {
    print for 1..3;
    print "\n";
}

foo for 0..9;
[download]

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