#!/usr/bin/perl
use strict;
use warnings;

my $dref = \&new_date;
my $fref = \&new_date_append;  

# call function foo, print different types of date
foo ($dref);
foo ($fref);

sub new_date {
 my ( $year, $month, $day ) = (localtime)[ 5, 4, 3 ];
 sprintf( "%04d%02d%02d", ( $year += 1900 ), $month + 1, $day );
}

sub new_date_append {
    my $date = new_date();
    return "OhioS___$date";
}

sub foo {
    my $date_fn = shift;
    print $date_fn->(),"\n";
}
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$dref=\&new_date is a reference to SUBROUTINE, $dref=\&new_date() is reference to the SCALAR returned by the subroutine