Your subroutines are said to be reentrant and (more specifically) recursive.

How does Perl handle this?

With ease.

I'm just wondering about the performance issues.

None. The first time a subroutine is called at a level of recursion it's never been before, there will be a tiny overhead as a new set of lexicals are created. These will be reused in future calls. 

my $c;
my %s;

sub foo {
   my ($x) = @_;;
   $c++;
   $s{\$x}++;

   foo($x-1) if $x;
}

for (1..1000) {
   foo(int(rand(6))+1);
}

print("foo() was called $c times, but only ", scalar(keys(%s)), " sets
+ of lexicals were created.\n");

[download]
foo() was called 4531 times, but only 7 sets of lexicals were created.

[download]

In reply to Re: subroutine calls itself by ikegami
in thread subroutine calls itself by tux402

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