Devel::Hints - Access compile-time hints at runtime


This document describes version 0.21 of Devel::Hints, released November 10, 2010.


    use Devel::Hints ':all';

    print cop_label();      # 'LABEL'
    # cop_label is only settable on Perl 5.8 or below
    cop_label(0 => 'FOO');  # "goto FOO;" is valid after this point!

    print cop_file();       # same as __FILE__
    print cop_filegv();     # same as \$::{'_<' . __FILE__}
    print cop_stashpv();    # same as __PACKAGE__
    print cop_stash();      # same as \%{__PACKAGE__ . '::'}
    print cop_seq();        # an integer
    print cop_arybase();    # same as $[
    print cop_line();       # same as __LINE__

    # cop_warnings() is only available to Perl 5.8 or below
    use warnings;
    print cop_warnings();   # same as compile-time ${^WARNING_BITS}

    # cop_io() is only available to Perl 5.7 and Perl 5.8
    use open IO => ':utf8';
    print cop_io();         # same as compile-time ${^OPEN}

        use IO => ':raw';
        print cop_io(1);    # access one uplevel; still ":utf8\0:utf8"


This module exports the cop (code operator) struct as individual functions; callers can call them to find out the lexical-scoped hints that its block (or statement) is compiled under.

No functions are exported by default. Each function may take an optional positive integer as argument, indicating how many blocks it should walk upward to obtain the cop members.

Functions can also take another optional argument, which (if specified) becomes the new value for the hint, affecting the current statement or block's behaviour.

On perl 5.10 or greater, the first argument to these functions can also be a coderef. In that case, they return the value for the first statement in the coderef's body, and if an argument is passed, they set the value for the entire coderef body. cop_line and cop_file are slightly special here - #line directives within the coderef will still be respected, and the line will be offset by the correct amount within the sub.



Label for the current construct.


File name for the current source file.


Glob reference to the current source filehandle.


The current package name.


Hash reference to the current symbol table.


Parse sequencial number.


Array base the calling line was compiled with.


The line number.


Lexical warnings bitmask, a.k.a. ${^WARNING_BITS}. If no lexical warnings are in effect, returns the global warning flags as an integer.


Lexical IO defaults, a.k.a. ${^OPEN}. If no lexical IO layers are in effect, an empty string is returned. Always returns undef under pre-5.7 versions of Perl.


Thanks to Rafael Garcia-Suarez for demonstrating how to do this with the elegant Inline::C code on p5p, which I adapted to this less elegant XS implementation.


唐鳳 <>

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To the extent possible under law, 唐鳳 has waived all copyright and related or neighboring rights to Devel-Hints.

This work is published from Taiwan.