use warning;
use strict;

{
    my %log_seen;

    sub log_info {
        # do not continue if done before
        return if $log_seen{(caller(1))[3]}++;

        warn(@_, "\n");
    }
}

sub f {
    log_info('some information');
    print "called f()\n";
}

f();
f();

__END__
some information
called f()
called f()