This is fairly simple. Represent your program as a graph. Each function is a node in the graph, and there's a directed edge from one node to another if the sub calls the other sub. Given this graph, calculate the transitive closure, and see if the transitive closure has a loop. The program is recursion free, if and only if the transitive closure doesn't have a loop, which is represented as a node having a link to itself.

Luckely, there's a module on CPAN that can help:

#!/usr/bin/perl

use strict;
use warnings;

use Algorithm::Graphs::TransitiveClosure qw /floyd_warshall/;

my $g;

while (<DATA>) {
    my ($from, $to) = split;
    $g -> {$from} -> {$to} = 1;
}

floyd_warshall $g;

while (my ($key, $value) = each %$g) {
    print "Recursion for function '$key'\n" if exists $g -> {$key} {$k
+ey};
}


__DATA__
aaa bbb
bbb ccc
bbb ddd
ccc ddd
ddd aaa
ddd eee
[download]

Abigail

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