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.IX Title "Expire 3pm"
.TH Expire 3pm "2022-10-13" "perl v5.34.0" "User Contributed Perl Documentation"
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.SH "NAME"
Tie::Hash::Expire \- Hashes with keys that expire after a user\-set period.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Tie::Hash::Expire;
\&
\&  my %test;
\&  tie %test, \*(AqTie::Hash::Expire\*(Aq, {\*(Aqexpire_seconds\*(Aq => 10};
\&
\&  $test{\*(Aqdog\*(Aq} = \*(Aqdoghouse\*(Aq;
\&  sleep 5;
\&  $test{\*(Aqbird\*(Aq} = \*(Aqnest\*(Aq;
\&  sleep 6;
\&
\&  print keys %test, "\en";       # The only key is \*(Aqbird\*(Aq
\&
\&  my %hi_res;
\&  tie %hi_res, \*(AqTie::Hash::Expire\*(Aq, {\*(Aqexpire_seconds\*(Aq => 5.21};
\&        # Decimal number of seconds works if you have Time::HiRes
.Ve
.SH "ABSTRACT"
.IX Header "ABSTRACT"
Hashes tied to Tie::Hash::Expire have keys that cease to exist 'expire_seconds' after their most recent modification or their creation.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Hashes tied to Tie::Hash::Expire behave like normal hashes in all respects except that when a key is added or the value associated with a key is changed, the current time is stored, and after 'expire_seconds' the key and value are removed from the hash.
.PP
Resolutions finer than seconds are available if the module finds access to Time::HiRes.  If Time::HiRes is available, you can expect expiration to be accurate to 0.001 seconds.  You may specify 'expire_seconds' to be decimal numbers like 5.12 .  If Time::HiRes is available, this number will be used precisely.  If you specify a decimal number and don't have access to Time::HiRes, a warning is generated and the code will function as though you specified the next higher integer.
.PP
The number of seconds specified by 'expire_seconds' is taken to mean an absolute maximum lifespan for the key, at the resolution described above.  In other words, if you set 'expire_seconds' to 1 second, and do not have Time::HiRes, keys could expire as quickly as the next machine instruction, but will not last longer than 1 second.
.SH "AUTHOR"
.IX Header "AUTHOR"
Jeff Yoak, <jeff@yoak.com>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2004 by Jeff Yoak
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.