gistfile1.txt

#!/usr/bin/perl

use strict;
use warnings;

use IO::File;
use IO::Dir;

my $base_dir = '/root/.cpanm/work/';

my $dh = IO::Dir->new( $base_dir );
while ( my $dir = $dh->read ) {
    next unless $dir =~ m{\A\d+\.\d+\z};

    my $build = IO::File->new( $base_dir . $dir . '/build.log', 'r' );
    while ( my $line = <$build> ) {
        my ($perl) = $line =~ m{on perl (\d+\.\d+)};
        if ( $perl ) {
            print "$dir -> $perl\n";
        }
    }
}