Example of caching a result within a file to be pulled later

cachedtime.pl

#!/usr/bin/perl
use strict;
use Attribute::Handlers;

my $cachettl = 30;

sub write_to_cache {
        my ($v) = @_;
        open CACHE, '>/tmp/cache';
        use Data::Dumper;
        $Data::Dumper::Terse=1;
        print CACHE Dumper( $v );
        close CACHE;
}

sub read_from_cache {
        # Check the staleness of a file
        my @stat = stat '/tmp/cache';
        return undef if time - $stat[9] > $cachettl;    # 30 second cache

        open CACHE, '</tmp/cache' || return undef;

        my $str = do { local $/; <CACHE>; };
        close CACHE;
        my $v = eval ( $str );
        return $v;
}

sub UNIVERSAL::cache : ATTR(CODE) {
        my ( $pkg, $sym, $code ) = @_;
        no warnings 'redefine';
        *{$sym} = sub {
                my $v = read_from_cache();
                unless( $v ){
                        my $r = $code->(@_);
                        write_to_cache $r;
                        return $r;
                }
                return $v;
        };
}

sub foo : cache {
        return scalar gmtime;
}

print "Getting the time... ", foo(), "\n";