The OPer seems to want to control one-time printing/logging from outside the package/module, so that approach would not seem to do the trick. (Also, I don't know what the  + in front of the  __FILE__ is supposed to do.)

One can play around with caller to get a general solution closer to what I think the OPer wants: 

# LogOnce.pm

package LogOnce;

use warnings;
use strict;

our @ISA = qw(Exporter);
use Exporter;

our @EXPORT    =   ();
our @EXPORT_OK = qw(log1);

my %once;


sub log1 {

    my $signature = join '|', caller;
    return if exists $once{$signature};

    return $once{$signature} = print __PACKAGE__, ": @_ \n";

    }


1;


# LogOnce.t

use warnings;
use strict;

use LogOnce qw(log1);


MAIN: {

log1('this should print', __FILE__, __LINE__);

t_log1_1('this should print');
t_log1_1('this should NOT print');

log1('this should print', __FILE__, __LINE__);

t_log1_2('this should print');
t_log1_2('this should NOT print');

log1('this should print', __FILE__, __LINE__);

}


sub t_log1_1 {

    log1('called at', __FILE__, __LINE__, ':', @_);
    log1('called at', __FILE__, __LINE__, ':', @_);

    }


sub t_log1_2 {

    t_log1_1('should NOT print', __FILE__, __LINE__);

    log1('called at', __FILE__, __LINE__, ':', @_);
    log1('called at', __FILE__, __LINE__, ':', @_);

    t_log1_1('should NOT print', __FILE__, __LINE__);

    }

[download]

In reply to Re^2: Why do I get a "used only once" warning here? by AnomalousMonk
in thread Why do I get a "used only once" warning here? by rovf

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